99 Ram 5.9 pretends to have turbo lag

[Bear_Gibson]

So as many of you may have noticed, my ole' dodge has been acting up lately. It all started a few weeks ago when I was heading to work. It drove perfect when I left, and then when making a left off the highway it was like the engine suddenly shrunk. It has no power on take off, after getting above 2000 rpms its like life is restored and we're making power again. I have checked the cat. Checked the plugs, replaced the plenum gasket. I've serviced and checked the transmission, I did find a broken 3-4 accumulator spring, but replacing that didn't fix the issue. I'm going to change the coil this evening. I haven't tested the fuel pressure. However, if it didn't have enough fuel at low speed to take off, then it certainly wouldn't have enough for higher speeds. I'm really at a loss here. No CEL light, no codes, it runs good other than pretending to be a go-kart engine with a monster turbo.

 

[Bear_Gibson]

Update, Fuel pressure is rock solid at 50 psi even while it's misbehaving.

No codes
Transmission shifts nice and firm
Back pressure is no more than 4psi
I've disconnected the evap line and ran it, no change. (Throttle port plugged)
I ran it with the pcv valve disconnected. (Intake port plugged)
I had the transmission shop look it over and check for codes, nada.
This started all of a sudden like one morning.
I've replaced the plenum, but it wasn't even blown.

I'm not sure what else it could be. It runs good, just without any real low end power. This thing use to kick you like a mule when it took off. Now it'd be lucky to turn the tires over in the mud.

 

[Sirriggs]

I was doing some searching around. Read this and see what you think? Its seems like your issue. His was under 3500 rpms

1999 5.9L (gas) - No power under 3500 rpm's

www.dodgetalk.com

 

[Bear_Gibson]

Yeah, even though my back pressure never gets above 4, I have read that in some vehicles thats bad. It was a new aftermarket cat 5 years ago. Logging the front and rear o2 sensor shows they have the same pattern. So at the very least it needs replaced. My plan is to convert it to a test pipe tonight. If that solves the issue, then it's time to build a new exhaust. I've been wanting to do true duals anyways. I just like that sound better.

 

[Bear_Gibson]

I can say with 100% certainty that it's not the catalytic converter.

 

[Sirriggs]

I was trying to do some research for ideas to help. I wished I knew what to actually look for. Even when I had some issues with the intake. I didnt see any huge loss of power. Tranny issues always the limp mode which is obviously something wasn't right.

 

[Bear_Gibson]

I really have no idea myself. Gonna, put my old 02 sensor back in because the new one doesn't seem to be switching properly. (torque live data) I'm gonna re-test the plenum to make sure it sealed properly. Trans shifts great, It just feels really weak at low engine speeds. The vacuum gauge was rock steady last time, indicating no valve issues. It runs smooth as silk, just with no real power down low. If it had a miss I'd say it's mechanical. I Just have no leads to go on.

 

[Sirriggs]

That's true. You checked the timing right? You said tranny was checked over by a shop. I wonder if your timing is off some? I hope this isnt a dumb suggestion?

 

[Bear_Gibson]

If the chain itself had slipped the computer would see that between the distributor sensor and crank sensor. The computer still shows the same timing as it always has.
Rechecked the intake yesterday, and it builds only 1 psi when tested without the pcv system hooked up.

 

[Bear_Gibson]

And the chain was new in 2016

 

[Sirriggs]

Im puzzled for sure. You would think something would trigger some kind of code. Man i wished I could help.

 

[Bear_Gibson]

It's fine. Even bench diagnostics help. It may give me an idea.

I have replaced the cat
O2 sensor
Map sensor
Tps sensor
IAC valve
Plenum gasket
Pcv valve

I've tested fuel pressure 50 psi rock solid

Vacuum gauge is as smooth as silk, although the point of no vacuum comes well before full throttle. Thats why I thought plenum gasket.

I did the plenum test last night, and it will only build 1 psi at 2000 rpms. The test I saw on YouTube showed it slowly building pressure at a steady rate. I'm wondering if i have a warped Intake. It only had a small amount pf oil in it. The oil consumption is only a quart an oil change. And the rear main leaks.

I'm very tempted to get another intake and have it checked for warpage.

 

[Sirriggs]

I was looking around back when I first had the issue of the broken bolt and to be honest, I couldn't locate one.( Intake). The couple I did find looked in worse shape. I was just lloking if it came to that. It seems some things aren't easy to locate but maybe that's because it being a 1999? The fuel rail looked to be rusted so I even looked for a new one and it seems that year was skipped parts wise. Thankfully it was surface rust so I sanded primed and painted it. For as many still on the road. I don't understand why so many parts are discontinued?

From what I read and you tube. The rear seal seems to be a simple change , just making sure to use something plastic so you don't gouge anything. As to the intake. Is that something that can be taken to a machine shop to see if they can check if its warped and see if its something that could be a simple fix? I know they can fix heads if they aren't too bad.

Don't feel bad. Drained oil pan of Marvin Mystery oil to do a good cleaning for new gasket and pan. The rain started so now I have to wait till morning. They are sitting in the cab of the truck. I can't win for loose at times. lol

 

[Bear_Gibson]

I can check for warpage with a good straight edge and feeler gauges. My biggest hang up is that this is my only vehicle, so when I tear into it i have to have all my parts to put it back together. I was hoping to find concrete evidence of what has failed. I might pull the cap and rotor to make sure there isn't an issue there this weekend.

 

[Bear_Gibson]

I have been using track recorder on the torque app to datalog sensor data. I need to save it to my computer so I can look it over. I read somewhere that theres a wire connection above the transmitter that is prone to corrosion and failure. Thus causing o2 sensor issues. I do seem to have some odd o2 readings. Both my old ntk o2 sensor, and new elCheepo give the same readings.

 

[Sirriggs]

Well I did find a intake manifold for about 140 bucks eBay free shipping if you ever need one. I'm lucky to have a ford truck that I use as a daily driver. Big part of why I'm trying to get the dodge up and driving because it was the wife truck and it really didn't have any real bad issues over the years. My thinking now is it didn't slip till I replaced that broken spring in the over drive so I'm hoping that once I do the band adjustment. That might solve the issue? Once the motor is back together, then tranny adjustments and fuel tank drop and clean system. Then I can do my fresh start and see how she acts. Then its normal things from sitting brakes, tires and fresh fluid change in rear end. Then go from there.

I'm crossing my fingers for you.

 

[Bear_Gibson]

At this point I'm seriously considering having a priest perform an exorcism on the dang thing. It ran perfect for years and then one morning it just had enough.

 

[Bear_Gibson]

If you drop the trans pan check to see if you're 3-4 accumulator spring is broken. Its a common failure

 

[Sirriggs]

Already did that and it was replaced. The slippage started after that but not to hi jack your thread either. I'm looking around to see if anything comes up that maybe can help you with your issue. If I remember there is some adjustments that can be done with the cables including tranny. I am wondering if maybe they are off enough to affect the throttle? Weather being dumb here with off and on showers , so this will give me something to do.

 

[Bear_Gibson]

I considered that too, but the tv (throttle valve) cable adjustment has been checked.