Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

[Bill Z]

Here is some dialogue from this past week. It says a lot about what is happening.

I just don’t know what to try now without just spending money replacing stuff that may be OK anyway.

Here is the start.

My current problem is a hesitation at off idle. Just as I try to give it gas. Even slowly. I have plenty of vacuum and fuel pressure. I checked the intake bolts too. I used DataMaster and checked to see if there was a dead spot in the TPS. Looked good. By the way, what is a good range for the TPS? I have .48 volts at closed throttle and 3.85 volts at WOT. I guess that is a TPS thing.

What else do you suggest I try?

Will a DataMaster log tell what the problem is? I notice that I have 18 whatever of vacuum then when I ease on the accelerator, the vacuum drops to almost 0 (in some cases (mostly when the air conditioner is on)) and no acceleration. Would all of this show up on DataMaster (I don't know what to look for)?

I checked the timing, vacuum lines, and tightness on the gasket bolts. All is OK.

I got an idea. How about real heavy grease around the TB butterfly shaft (like Plummer’s grease)? If the problem goes away, then it is the TB. If the problem stays, even a little bit, then it is something else. I will try it today and let you know how it went.

OK, here is what happened when I greased up my TB shaft. I got almost 1.5 more vacuum (almost 20). Shows me there is an issue there. However, I still have a little hesitation (still some other problem). I'll agree that the vacuum leak does aggravate the other problem.

One thing that I didn't do and am doing now is disconnect the ECM. I remember the ECM tries to remember things. On my last test, the idle was somewhat fast. The ECM didn't compensate for the better vacuum (I figure). I will try another test in a few minutes.

It’s running smoother now with less hesitation.

Now, when my truck gets hot, it really starts running like crap. It bucks and stalls. Especially when the air conditioner is on. It can’t even make it across the intersection. I have to turn the air off and rev up the motor (won’t rev with air on) to clean it out enough to get across the intersection. Talk about embarrassing. It’s that off idle problem but much worse. It seems to run OK when I can get the RPMs up.

Since I have an oil temp gauge, I will give oil temps here. When the oil temp gets over 175 degrees the problem starts. Most days it never gets that high because I drive from the house to the park and ride (all of 2.5 miles). However when I have to go to church or someplace a few miles away, it gets hot.

I am thinking it may be electrical of some sort. Maybe a sensor getting too hot and messing up. May be the module in the distributor failing under heat (maybe not enough heat compound under it).

When I got home and put DM on it, the only code was 34 MALF O2 Rich. Makes sense. It felt like bogging down. But why?

Also, (Maybe associated) it seems to have a similar problem with hesitation right during a sharp turn as you are accelerating to get out of it. You know what I mean. I thought it might be gasoline shifting and the pump going dry but I kept watching the fuel pressure and it didn’t change when it was happening. Same as the first problem, no change in fuel pressure.

It is getting to be summer. I have to have it running to get me around. Have to be more than a winter truck.

Maybe all of the above is too much information.

Any ideas or test I should run to figure this out?

Just what to try now?

 

[gjp]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

sounds like what I have. I cant figure out my problem. Check the grounds. have you looked at the plugs?

 

[QUICK STORM]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

did you change the fuel filter?

 

[jjorgensen52]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

similar to what I have as well. mine presents as irratic idle, stalling and dropping a cylinder when coasting. I have yet to figure it out either. Checked for vacuum leaks, checked plugs, new wries, new dist., new coil, etc. AFR stays constant when it happens.

:2cents: if the Coolant temp sensor isn't working properly the truck will never come out of the warmup cycle, and as a result it won't ever lean out ... which would explain the bogging down ... it would also cause, I believe, the sluggish fuel response (open loop fueling) when accelerating.

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

:2cents: if the Coolant temp sensor isn't working properly the truck will never come out of the warmup cycle, and as a result it won't ever lean out ... which would explain the bogging down ... it would also cause, I believe, the sluggish fuel response (open loop fueling) when accelerating.

Does the coolant temp value show up on DataMaster? If DataMaster shows that it is warming up then it must be working. Right? I will check.

QUICK STORM mentioned checking or changing my fuel filter. If the fuel filter were clogging up, wouldn’t my fuel pressure drop? It doesn't.

On the way to work today, I thought of the oil pressure switch. When the engine gets hot the oil gets thinner even though I am running Mobile 1 20W50. Maybe it is at that low area where the switch just is or isn't ready to switch.

More thoughts are appreciated.

 

[SBNova]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

I am not sure about the factory TPS voltage setting for a Ty, but for my Vette which uses the same TB, the setting is 0.54 volts with the key on engine not running. I have my Ty set at .54 and it improved alot from the setting the previous owner had it- something like 0.62. A little can go a long way on driveability with a TPS setting. Give it a try.

 

[bjk_typhoon]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Did you try the bike inner tube test yet. Buy a replacement inner tube, cut out a section with the valve stem still in place. Pinch off on one side (roll up and clamp off) and stretch the other side over the intercooler inlet. The apply air pressure (without motor running) and listen / feel for leaks. I had my throttle body rebuilt and it leaks worse now that it did before. I believe that is why I am recieving the same symptons that you are but have not had the oppertunity to fix it yet. Just another idea to try.

 

[jjorgensen52]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Does the coolant temp value show up on DataMaster? If DataMaster shows that it is warming up then it must be working. Right? I will check.

QUICK STORM mentioned checking or changing my fuel filter. If the fuel filter were clogging up, wouldn’t my fuel pressure drop? It doesn't.

On the way to work today, I thought of the oil pressure switch. When the engine gets hot the oil gets thinner even though I am running Mobile 1 20W50. Maybe it is at that low area where the switch just is or isn't ready to switch.

More thoughts are appreciated.

It does show up, but it can give a bad reading for sure. My truck is now not going into closed loop either, running a 10.5 AFR on the highway and knocking like crazy... I have no trouble idling though, it leans up to 13 - 14's at idle for some reason

 

[QUICK STORM]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Does the coolant temp value show up on DataMaster? If DataMaster shows that it is warming up then it must be working. Right? I will check.

QUICK STORM mentioned checking or changing my fuel filter. If the fuel filter were clogging up, wouldn’t my fuel pressure drop? It doesn't.

On the way to work today, I thought of the oil pressure switch. When the engine gets hot the oil gets thinner even though I am running Mobile 1 20W50. Maybe it is at that low area where the switch just is or isn't ready to switch.

More thoughts are appreciated.

i believe a clogged fuel filter will effect volume(flow) not pressure, but i could be thinking backwards as always:roll:

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

i believe a clogged fuel filter will effect volume(flow) not pressure, but i could be thinking backwards as always:roll:

Fuel filter will effect both pressure and volume to some extent (determined by how clogged the filter is). Fuel filter issues tend to show up when volume and pressure are more important, like higher RPMs with load. My problem is at off idle where the problem goes away at RPMs above 2000 RPMs. This is why I discount the fuel filter. I could be encouraged to re-think all of this.

 

[93TyGuy]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Have any of you guys checked your ignition control module? They like to make all kinds of hell when they get hot. Pain in the ass to change but its worth having it checked out. Just my :2cents:

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Have any of you guys checked your ignition control module? They like to make all kinds of hell when they get hot. Pain in the ass to change but its worth having it checked out. Just my :2cents:

I plan on doing that this week end. I was going to take it out and take it ot the local auto parts shop. They have a tester. I plan on connecting it up, turning it on and hitting the module with a propand torch because it only goes to shit when it is hot. I will take pictures of the guys at the counter when I do it.

 

[93TyGuy]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

I plan on doing that this week end. I was going to take it out and take it ot the local auto parts shop. They have a tester. I plan on connecting it up, turning it on and hitting the module with a propand torch because it only goes to shit when it is hot. I will take pictures of the guys at the counter when I do it.

You wont have to torch the poor thing. It will get hot just by running it on the tester. Let them run it about 3 times or more and then you can torch it. :rock: :woot: :devil: :microwav:

 

[gjp]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

My problem was a clogged filter and a bad AFPR.

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

I got it fixed (for now anyway). The problem was a vacuum leak around the shaft that holds the butterflies in the throttle body. I got a TB with many less miles on it, cleaned it up a little, stuck it on, connected DM up to the truck and adjusted the IAC and TPS. Another thing: to improve the vacuum on this newer TB and to reduce ware, I used some high temp Plummer’s grease and packed it into the shaft where it comes out of the TB next to the butterflies. I mean that I pressed it in and kept pressing. I then wiped off the excess grease so it looks clean. Now at idle I have just over 20 bars.

This all didn’t just work first thing. There was some difference in the engine and the TB adjustments that the guy that I bought the TB from. I hooked up DataMaster and noticed the IAC count was zero and I had a code 34. The TPS was way over to .59 volts. The plug to the throttle return stop was missing from the TB. So I cranked it back till I got .49 Volts. This caused the IAC to start working. I got it to 28.

I took a test drive and it was nice. Still an issue of a slight bough when I turn a corner (I figure a different problem).

Just wanted you guys to know.

 

[Grn93Ty]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Bill Z, glad to hear you solved your hesitation problem.
My Typhoon has very similar symptoms to those described by you. With my truck, the off idle hesitation occurs at random. I can drive it 10 times and it may occur once or twice. But once it starts acting up, the problem won’t go away until I shut it off and let it sit for at least an hour.
Also, the hesitation only happens after I’ve driven for at least 30 to 45 minutes and the hesitation is always accompanied by backfire. However, if I floor the accelerator, the hesitation problem would disappear, but flooring it isn’t always practical.
I’ve discussed this problem with others and was told by a very reputable person that my hesitation problem may be a faulty fuel injector. Unfortunately, I haven’t had an opportunity to check the injectors yet.
I just wanted to say that I’m glad I found this topic and I’m going to try some of the suggestions mentioned, including your solution.

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

I just wanted to say that I’m glad I found this topic and I’m going to try some of the suggestions mentioned, including your solution.

Try the grease first (see my post above). It is real cheap. If you don't notice any diff then it probabily not your TB. Verify with DataMaster.

Good luck.

 

[Black Knight]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

Hey Bill Z I was having a problem similar to what you where describing and it turned out to be my distributor was bad, when I pulled it out it literaly broke in two pieces in my hand. I dont know how it ever ran?? Anyway put in a new one and have had no trouble ever since, except for a slight miss I still haven't looked into. HTH

 

[Bill Z]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

One of the first things I did was to do an ignition module swap and to check out the distributor. That was eliminated as not being one of my problems right a way.

Yours was broken? Strange. Very strange. Good that you fixed it.

 

[purdaddy]

Re: Runs Bad at Off Idle when It Gets Hot. Need Pertinent Suggestions

My Ty exhibits this same sort of condition. Only when it's hot out (85 degress farenheit or so) and I've got it up to (and often a little over thanks to A/C and ambient temps) normal operating temp. Are you saying that the problem (at least with yours Bill) was essentially due to boost leak of sorts at the Throttle Body itself? Possibly from the engine compartment getting so hot that the metal expanding (too much) could be causing it?? If so, wouldn't there be a way to test that by finding some mechanism to keep the TB cool(er)? I was leaning towards trying to find a way to keep everything (especially the engine and intercooler coolant temps) down.

I'd love to be able to drive the Ty in the summer w/o looking like an idiot bucking and stalling all over the place when it gets hot......
Thoughts, comments, flames?