'88 W100 318/2 barrel throttle body surging extreme loss of power, please help!

[nikwho]

Hello all,
I've searched and read, and read. But, I'm still stumped. I don't want to just throw parts at it. So, this is my 17 year old sons truck. He bought it from my wife's dad. It's a really cool short bed 4x4.

So, at first, my son called me and said that his truck wouldn't start one cold morning. Then, he'd get it to start, but ran super rough. He pulled the air cleaner and noticed that only one fuel injector was spraying. We pulled them both out and one functioned well with power applied, the other immediately started smoking and did not open. So, we replaced just the non functional injector. My son was super anxious to get it together, so he reassembled while I was at work.

It fired right up, but was underpowered. I realized that we had not replaced the fuel filter. So, I asked him to swap that out, which he did.

This is the point where we could have easily determined if we were good to go, BUT, this is also where he got impatient and began to pull his stock exhaust system off and install a set of headers that we bought him for his birthday. He is very mechanically inclined, and in his third year of auto shop in HS. He didn't realize that if we had issues, it would make it harder to determine our problem.

Anyhow, he got the headers installed, I helped him weld an O2 sensor in the header collector, and we welded up a dual exhaust system. No Catalytic converter! We cut the wires for the one upstream O2 sensor and extended them, as the factory manifolds had the o2 sensor higher up in the system. But, sensor is installed.

Truck fires right up, but surges and hisses, stalls and backfires. Just runs like crap. I just ordered a new o2 sensor, as I think that the current one may be original to the truck. We ha to spray some PB blaster on the inside of the manifold to get the sensor broken loose. Not sure if that's hurt it. So, going to replace o2 sensor to see if that helps.

This has a non-vacuum advance distributor. The time was off a little (I warmed it up, unplugged coolant sensor & timed it to 10 before TDC). I still worry that it may have jumped a timing gear tooth, but would I be able to time it correctly if it had?). It doesn't seem to have a misfire, though I am thinking that a new cap, rotor, plugs and wires are in order.

I have also replaced all vacuum lines, using the Haynes manual to follow each line. It was a mess. Like, I'm surprised it ran, in the state that the vacuum lines were in. So, those are all new. I unplugged the throttle position sensor and it ran worse and would immediately die when I would touch the throttle.

Also, this truck doesn't have a Check Engine light, the best that I can tell! I tried to read the codes with the key on/off/on/off/on method, but realized that I didn't see a check engine light when I turned the key on. So, I took the dash apart and pulled the instrument cluster. It has a "Maint Req" light (I've read it serves as a reminder to check emissions, but isn't an error light), Oil Pressure light, and right where I thought that the check engine light would be, there is a "Gate Open" light, I'm assuming would be for a Ram Charger. It had a fourth light, but I'm forgetting what it was at the moment. Anyway, I removed all bulbs, verified that none of the four lights were Check/Service Engine lights and swapped the bulbs with known working gauge light bulbs.

So, how can I check codes in a Pre OBD-II truck, that doesn't have a check engine light? I'm stumped. I'm thinking that maybe the gauge cluster was replaced at some point?

I'm stumped, feeling like I'm not very competent and would greatly appreciate any help that could be offered! I don't really want to take this to a shop. I would like to walk through the diagnosis of it with my son, for a teachable moment.

Thanks so much,
Nik

 

[nikwho]

Sorry for the novel! I just looked at it after posting and realized how long it had gotten!

 

[crazzywolfie]

the check engine light is on the panel above the heater control. it may have a burnt out bulb since it comes on everytime you start the vehicle.

did you make sure to order a ntk o2 sensors? o2 sensor can be a nightmare to change on these thing. i used a pipe wrench on my 93 and thought i thought i was going to break it trying to get it out. i don't know if it would be the same on 88 as it would be on 89 but i think they did originally planned on putting the o2 sensor in on the y pipe after where the 2 pipes meet which is why there is a o2 sensor plug somewhere on the passenger side of the engine with an extension cord plugged into it to run back to the drivers side manifold.

 

[nikwho]

Thank you so much for the reply! And for showing me where the check engine light is! I had watched a video from probably a different year truck that showed the service engine light on the dash! I was super bummed when I couldn't find it. So, I'll pull the dash back apart and replace the check engine light bulb! That will allow me to finally get some codes out of this thing! That may tell us a lot.

Okay, we have changed the o2 sensor. Idled rough for the first few minutes, but then cleared up, as I kind of expected. I was excited and went to pull it out of the side yard, and into the drive way and realized that it had a pretty extreme lack of power.

I had to feather the throttle between a very fine line of trying to get it to move, and dying! If I have it just a hair too much throttle, it would die!

We have replaced the fuel filter as well. Also went through the throttle body, cleaned, replaced one of the fuel injectors and put back together. Both fuel injectors are squirting what seems to be equally.

So, I feel like the issue is with a sensor. It doesn't feel like it has a misfire. It runs smoothly at idle and at higher RPMS when not loaded. It bogs and will die almost before it moves in drive or reverse. It revs strongly in neutral, too! It seems as though something is conflicting when under a load. Like, a bad sensor. I was thinking the Throttle Position Sensor was a culprit. When the truck is sitting and idling nicely, if I pull the TPS, the truck will die right away. Not sure if that tells anything. Truck dies immediately if I pull the vacuum hose off of the EGR valve. Again, not sure how indicative that is of anything, or if that is a normal finding?

 

[crazzywolfie]

unplugging sensors can cause also sorts of weird things to happen. it almost sounds like a TPS in some ways not not others. i am pretty sure you can test the TPS with a mult meter to see if it is operating properly.

 

[nikwho]

unplugging sensors can cause also sorts of weird things to happen. it almost sounds like a TPS in some ways not not others. i am pretty sure you can test the TPS with a mult meter to see if it is operating properly.

I thought the same thing. It sort of acts like a TPS, but not really exactly what I'd expect a failed TPS to do. I don't want to just aimlessly throw parts at it. I just started a 48 hour shift at work, so I won't be able to mess with it again until Sunday. I may price out a TPS and if it's not too spendy, I may just replace it, as I have read about a lot of trouble coming from those. I'm all for throwing parts at it that commonly fail, just to potentially prevent future issues.

Nik

 

[DustyDog99]

An easy way to check if you have skipped tooth on the timing is to bring it to top dead center on the timing marks and see how far off the rotor is. The way it sounds, I believe it is a timing problem. How many miles are on the truck?

Sent from my SM-S727VL using Tapatalk

 

[nikwho]

158,000 on the clock. Not too high. So, I timed it to 10 degrees BTDC with a timing light and coolant sensor unplugged, after warming up. It took just minimal adjustment to get it there, like 2-3 degrees worth of adjustment. Would you still be able to get it timed successfully if it jumped a tooth? I have no idea. I would think you would, but the cam and valve timing would just be off. It honestly seems to run to well in neutral for the timing to be off enough to take virtually ALL power away in gear. It just feels like a sensor, with the way that it's acting. But, I honestly have no idea!

 

[nikwho]

An easy way to check if you have skipped tooth on the timing is to bring it to top dead center on the timing marks and see how far off the rotor is. The way it sounds, I believe it is a timing problem. How many miles are on the truck?

Sent from my SM-S727VL using Tapatalk

I want to make sure that I'm thinking of this correctly. So, you're saying to get a cylinder (say, #1) to TDC on the compression stroke, then verify where the rotor is pointing. Where the rotor is pointing would directly correlate to the flashes of a timing light, so it seems that this procedure would tell you essentially the same thing that a timing light would, which in my mind is the timing of the distributor to the crankshaft. If a timing chain slipped a tooth, it would lose the timing associated with the camshaft, which also is what drives the distributor. So it seems that either test would show the same results.

Now, I JUST remembered from thinking this through, that the truck was actually showing more like 25-30 degrees BTDC when I initially checked with a timing light, so the couple of degrees that I gave in my previous post is incorrect! That bigger discrepancy tells me that it could have jumped a tooth! I was able to adjust the timing back to 10 degrees BTDC. So, that would make just the cam off, which could definitely kill power! I would expect it to run worse being off that much.

How do these engines run when jumping one tooth? Guess that it might be a good time to grab a timing set! Do these engines use Hydraulic flat tappets, Or were they roller lifters by 1988? Might be a good time to get a mild "RV" type cam, new lifters and a timing set. If I'm going in that deep, might be worth a cam swap.

Hmm.

 

[crazzywolfie]

if the engine is factory it should have a roller cam. also since it is TBI you can't change the cam in it because the computer would not know what to do.

 

[nikwho]

The more I learn about this truck, the more I want to buy a vacuum advance distributor and a carb intake and just throw a 600 car Edelbrock carb on it!

 

[nikwho]

Okay, a little update in this rig. Replaced O2 solenoid and TPS. TPS came up a bunch with multiple folks that I talked to. They are a frequent offender with these trucks and not that expensive, so I'm okay with throwing that part at it. Truck has 158K miles on original O2 sensor, so that was due anyway.

Now, I have also replaced the old Check Engine light bulb and ran the codes.

I got: 12, 37, 55

So,
12- PCM power disconnected. (Me changing battery, likely?)

37- Torque Converter clutch solenoid CKT or park/neutral switch failure.

55- end.

So, now that the o2 sensor has been replaced, it idled and runs very nicely. This has been difficult, I believe, due to compounding issues, that made the problem more clear after replacing the o2 sensor.

Seems that it's running nicely but thinking that it's still in park or neutral when it's in gear maybe?

Though, it pops, spudders and dies when given throttle in any gear, not just in forward/reverse gears OR just in park/neutral.

Does this seems like torque converter clutch solenoid CKT? What does CKT stand for?

Or does this sound like more of a park/neutral switch failure issue?

Thank for any help!

Nik

 

[nikwho]

I'm thinking that it has nothing to do with the park/neutral switch, as it will only crank the starter in park and neutral, and not in any other gear. Though, I may be off with that theory. It may control more. Whatever it is sure seems to be effecting more than just the transmission. If it was a torque converter clutch solenoid issue, I would think that it would not have any issues whatsoever in park or neutral.

We may still have compounding issues that are making diagnosis difficult. Guess I Just try to chip away at stuff, or it may just be time to take it into a shop.

 

[nikwho]

I also just read that code 37 can be responsible for "Part throttle lock/unlock solenoid driver circuit (87-89)"

So, seems as though this code may indeed be the issue with this truck.

 

[crazzywolfie]

did you check the hall effects sensor in the distributor? 12 37 and 55 are nothing to worry about. the only connector on your trans should be the neutral safety switch

 

[Ogpro]

Bummer? I find alot of these,
Almost exactly my problem without a solution, must be the last part to get replaced?
Any body have an engine electrical schematic for this truck?
Mine is an 88/318, but the electrical schematic i have is missing the temp sensor on the tb.
I beleive it may be late year or early 89 electrical setup.
I have hot start issues, and twice in 2 years ive had total loss of power.
Power loss occurred when under load and hot outside temps but engine temp at normal operating temp on guage.
The temp sensor for guage is new
O2 replace a few weeks ago as exaust was smelling rich and was a bit under powered.
Last time couple years back i replaced temp sensor in tb unit because of hot start issues, didnt help any, after good run 10 2 12 miles drive and shut down,
It has trouble starting, i will turn on ignition listen for idle air solinoid to set watch temp guage on dash rise to mid point on guage then shut down ignition.
I do this twice then try crank, wait and repeat usually starts third or fort time around.
Runs fine other wise.
Other day was hauling 4x8 trailer 2000lb of rock, about 1000 feet from my gate there is a bed of sand i drive through in first gear, half way through it starts bucking, so i clutch and feather through but have severe lack of throttle responce , only a bit of just off idle and then nothing. Its up hill in my drive way
I get it through the gate and it dies.
Wont hold idle.
Like the last time this happened, it sat for a few hours, started right up, drove up the hill and parked it. No problems with drive ability, the radiator was replace 5 years back normal temps 180/190 running range temps were fine when the issue occurred.
One normal/ abnormal occurrence that happens most days on startup and driving is, as the truck is driving out when warming up, it will get a bit of bump in idle and power after a few minuts, this is not quite halfway to normal temps.
Im trying to debug this truck and need an accurate electrical diagram of engine compartment.
As for codes nothing.
Also, on most of the forums iv seen posted a code list for dodge trucks, that is the list for dodge cars, the truck list has variations like ac fan relay i beleive 34? Is actualy idle control on trucks
Its the only code i remember but may be wrong.
I will repost as another link with what iv got.

 

[Ogpro]

Here is 88 electric without tb temp.

 

[nikwho]

Well, to provide a bit of an update, I ended up taking my sons truck to the shop. They diagnosed it as the computer being "fried". They wanted $2500 to swap it to a carb. Said that they couldn't source a new ECM. They stated that the computer was no longer able to adjust the timing adequately. I took that as sounding reasonable, as I couldn't figure it out. I brought the truck home and we swapped it over to carburetion ourselves.

However, once we got half way through the swap, when I had the accessories all off of the front of the engine, we were a water pump away from the timing chain. So, I thought "why not check it?". Well, it was super loose! It was off two full teeth, as far as I could tell, but it could have been a full rotation, PLUS two teeth! Which would explain it running progressively worse, until it would no longer run.

So, we were considering this swap prior to having this issue, and we were half way through the swap before realizing that the timing chain had skipped teeth.

I believe that our problem entirely came from the timing chain. So, while it was apart, we changed the timing set. If you haven't verified that the timing set is good, I would start there! These timing sets are notorious for becoming loose, because of the weird vinyl cam gear. A new double roller timing set cost me about $40.

We ended up completely bypassing the computer in my son's truck. We installed a set of Heddman headers, Weiand aluminum intake manifold, Edelbrock carb, Holley fuel pressure regulator and haven't looked back. After the truck started making really good power, the transmission could no longer hang on. So, a couple of weeks after the swap, the transmission shat itself out on the side of the road! We had the transmission rebuilt and reinstalled it, then the starter went out, along with the cheap voltage regulator! So, after cooking a battery, and frying my sons new Sony stereo, we finally checked the alternator's output while driving. It was charging between 19-21 volts! So, now we had to buy a new stereo and battery.

All of this is after we had to go through all of the brakes, replace the leaking radiator and heater core, along with going through about every other system in the truck! I'm into this truck for about $4,000 over the past year and a half! But, I'm too stubborn to give up now! I won't allow it to beat me... at some point, the truck HAS TO stop breaking down! LOL.

At any rate, good luck diagnosing your truck! I would strongly suggest verifying your timing set is good before committing to any other major repairs.

Nik

 

[Skatulaki]

Sooner or later you will win and breath a great sigh of accomplishment, and your son will get many valueble lessons and an education in the process!

 

[1970Pelle]

Fuel pressure reading ? What do you have? You need to know what the fuel pump is doing. If I missed it, I apologize. But remember the basics first, spark, Fuel, Compression. If you have these three things then move on in your diagnosis.
crazzywolfie seams to have the knowledge to get you straighted out.