Hard start arm 1996 5.2

Whitedog · Jun 18, 2017

Greetings. Truck is a 1996 5.2 98,000 miles, MANual transmission, stock. The only work I have done on it in the past months has been changing the track bar.

I don't drive this truck very often, but recently it has been giving me some fits. First start is perfect, but the second start is probably going to be a hard start. I have to step on the loud pedal and hold it and feather it to get it to start, then if I don't keep on it, it will die. Once it clears up, it runs fine.

No CEL, but I haven't checked for non OBD codes. I have a fair scanner and I should be able to get some good data, but I'm not sure what to look at or what to expect. I haven't had any troubles with this truck so I haven't had to work on it meaning I don't even know if it's drive by wire or cable so I don't know if it has an IAC valve. I'll have to check it out next time I get to the shop.

So, any advice? I searched the titles for "hard start" but didn't find anything relevant.

BTW, it is a hard start warm.

dapepper9 · Jun 18, 2017

Iac is common for such things

Whitedog · Jun 19, 2017

Yeah. I've chased IAC problems on other rigs and that was the first thing I was going to look at when I find that time. So maybe October...

dapepper9 · Jun 19, 2017

Other possible issues can be 02 and tps

Whitedog · Jun 19, 2017

While trying to start, the TPS has no effect but once it is barely running, it does work. It seems to me that this should eliminate the TPS. Do you agree?

dapepper9 · Jun 19, 2017

Whitedog said:
While trying to start, the TPS has no effect but once it is barely running, it does work. It seems to me that this should eliminate the TPS. Do you agree?

Should yes but oftentimes tps failure gives a false throttle indication both at idle and starting cancelling out iac and causing starting and idling issues.

Whitedog · Jun 21, 2017

dapepper9 said:
Should yes but oftentimes tps failure gives a false throttle indication both at idle and starting cancelling out iac and causing starting and idling issues.

LOL thanks for the definitive reply.

I'm a Diesel mechanic so I understand what you mean. It is intermittent now, or maybe it just happens in a certain situation like the second start after running for 5.5-12.75 minutes. Yeah... Very definitive problems deserve very definitive answers, but as you know, nothing on cars is definitive.

Now I just need to do more testing to try to narrow down exactly when this happens so I can be ready with my laptop to get data when it's failing.

Hopefully I'll remember to keep you updated on this so I dont leave you hanging.

dapepper9 · Jun 21, 2017

Whitedog said:
nothing on cars is definitive.

Especially when electrical lol. I fix airplanes so yeah same boat. I hate electrical lol.

But you can rule out tps if you can watch throttle percentage when you're in such situations. Range is 11-12ish% when off, 13-14ish% at idle, 75ish% at WOT. Anything above about 15, MAYBE 16 will point at a tps issue.

No issue there clean the iac by spraying down the pintle with carb, brake, throttle body cleaner. Any will work fine thru won't degrade it. Don't move the pintle though

Shadow_Death · Jun 21, 2017

Testing the TPS is easy. Just probe the back of the tps plug using a multimeter. An analog one is preferred but not really needed in your case.

Plug the negetive lead into the back of the plug where the black wire is on your tps. Then plug the positive lead into the plug where the center wire goes in. Basically back probing. Tlset the multimeter to DC and turn the ignition to on, don't start the truck just on.

Your voltages at idle should be more than 0.2v and less than 0.8v I believe. Max voltage at wide open throttle should be no more than 4.8v.

Edit: You could test it with the truck running as long as you make sure the leads won't drop into the belt.

Sent from my Nexus 6 using Tapatalk

Whitedog · Jun 21, 2017

I couldn't get a reliable connection by backprobing so I pulled the connector apart and went direct onto the terminals after I plugged them in. At idle it was .7 VDC and at WOT it was 3.8 VDC while starting like dog Doo.

Something that you reminded me about talking you a were talking about voltage is that I think my POS battery is bad. It cranks over slowly and if I leave the lights on for just a few minutes, it will barely turn over and start. I watched voltage at cranking and it dropped to 8.XX so I know the battery is weak at best. I need a good battery but I'm not sure I need an IAC. So I think that I will start with the battery and see where it goes from there.

Once running, it charges at 13.8 VDC. I don't know ow if that is low or not.

dapepper9 · Jun 22, 2017

Shadow_Death said:
Testing the TPS is easy. Just probe the back of the tps plug using a multimeter. An analog one is preferred but not really needed in your case.

Plug the negetive lead into the back of the plug where the black wire is on your tps. Then plug the positive lead into the plug where the center wire goes in. Basically back probing. Tlset the multimeter to DC and turn the ignition to on, don't start the truck just on.

Your voltages at idle should be more than 0.2v and less than 0.8v I believe. Max voltage at wide open throttle should be no more than 4.8v.

Edit: You could test it with the truck running as long as you make sure the leads won't drop into the belt.

Sent from my Nexus 6 using Tapatalk

I personally don't like the multimeter method simply because it's easier to read the pcm throttle percentage when starting or driving vs trying to probe it. Tools like the TorquePro App and a Bluetooth dongle for the obd2 port are awesome for things like this. At the same time you're reading throttle percentage you can read how much vacuum you're pulling. Low vacuum can indicate either a leak (not really all that detrimental on these) or cam also point at the iac opening too far. Higher than normal vacuum could indicate it's not opening enough

dapepper9 · Jun 22, 2017

Whitedog said:
I couldn't get a reliable connection by backprobing so I pulled the connector apart and went direct onto the terminals after I plugged them in. At idle it was .7 VDC and at WOT it was 3.8 VDC while starting like dog Doo.

Something that you reminded me about talking you a were talking about voltage is that I think my POS battery is bad. It cranks over slowly and if I leave the lights on for just a few minutes, it will barely turn over and start. I watched voltage at cranking and it dropped to 8.XX so I know the battery is weak at best. I need a good battery but I'm not sure I need an IAC. So I think that I will start with the battery and see where it goes from there.

Once running, it charges at 13.8 VDC. I don't know ow if that is low or not.

If you have a weak battery thats the first place to start. Batteries can do weird **** to these things. It's normal to see a bit of voltage drop when cranking but 8s sounds low. While running and charging you're pretty close to within range.

Once batteries get hot they become less effective. Don't hold a charge as well, can become prone to voltage drops until alternator brings it back in line, etc.

Shadow_Death · Jun 22, 2017

dapepper9 said:
I personally don't like the multimeter method simply because it's easier to read the pcm throttle percentage when starting or driving vs trying to probe it. Tools like the TorquePro App and a Bluetooth dongle for the obd2 port are awesome for things like this. At the same time you're reading throttle percentage you can read how much vacuum you're pulling. Low vacuum can indicate either a leak (not really all that detrimental on these) or cam also point at the iac opening too far. Higher than normal vacuum could indicate it's not opening enough

Yup, I use BAFX and Torque Pro all the time. I just recommended the Multimeter test as a second reference.

Whitedog · Jun 22, 2017

Sorry about the rough post there. My phone thinks it's smarter than I are...

Anyway, I know that charging systems have different charging rates and I usually like to see over 14 VDC but maybe this vintage Dodge is different?

Anyway, after unhooking the TPS connector with the key on, it tripped the CEL, so if I have a code for the TPS, it was probably self induced.

Great way way to get definitive data, eh?

Shadow_Death · Jun 22, 2017

Well the upside is your original post said you didn't have any cels. So you could clear them and just keep an eye on it as you diagnose.

Edit: Fixed spelling.

Whitedog · Jun 25, 2017

The new battery certainly helped with the reluctant cranking.

*Note to self: don't buy Centennial batteries anymore.*

I still have to drive it hither and yon to see how the idle does. I bought the IAC just in case so I'll just throw that on if it continues to give me troubles.

Thanks for the help and support so far. It's been great.

Whitedog · Jul 1, 2017

Additional note to self: turn off the headlights after you install a new battery.

Gr8bawana · Jul 1, 2017

Whitedog said:
Additional note to self: turn off the headlights after you install a new battery.

Oh crap!

Whitedog · Jul 6, 2017

The new battery seems to have solved the problem. I will update if something changes.

Thank You all very much for your help and time.

Hard start arm 1996 5.2

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