Warm/Hot Weather Re-start Problem

New member here, glad I found this site! I've got a '96 Roadmaster Wagon (175,000 miles) with a number of original engine issues/codes. I'm not the mechanical-type, so I rely on others for repairs, and have recently had new plugs, wires, fuel filter done. One pressing problem not addressed yet is a re-start problem that occurs only when the outside temperture is warm or hot (70 degrees and up). When the car is turned off and sits for an hour or more, after having been driven at normal engine operating temps, it will sputter, idle rough, sometimes cut off and even backfire when it is re-started. If the engine is left to sit while idling rough as described, it will soon clear itself and idle/run normally after a minute or two. I have been told by a couple of mechanics that it sounds most likely the distributor is the issue, possibly the throttle position sensor also. Doe this sound correct? Also, is there a way to isolate/test the distributor as the cause without goitn through the water pump removal to get to the distributor? Thanks!

Since you have a Roadmaster, you can see your trouble codes in the climate control. If you post the codes here, people who are much better mechanics that I am will be able to point you in the right direction.

Here's how:
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Nick do you think he will be back?Wish him luck,at first I thought it might be Big Kahuna
from the SS forum playing a joke or something but I realized immeidiately that he was a
newby.
Jim Gordon

I considered that it might be BK, but decided it wouldn't be. My take on him is that he enjoys playing a jerk on the ISSF, but isn't really a jerk in real life. Showing up on a wagon forum just to troll would be a jerk move.

If you were driving a 91-93 ( instead of a 96) , I would suspect it would be the ignition module in the distributor. That used to happen to me until I mounted it remotely last year. You have the optispark system which I am unfamiliar with, but still suspect it as the cause.

You might also check the other forumn and search for optispark symptoms. it's also referred to as "opticrap" many times as well. They have a much larger database than we do., due to the fact there are more Impala fans out there than there are wagon nuts.

go down a ways on this page to find the optispark stuff

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Dave Buchholz

No BK here, just a newbie with a close-to same name...will try and go through the code viewing display on my climate control and post them up. Like I said, I'm no mechanic and all the codes are a little confusing to me! Do have a written copy of the codes and his description my auto repair guy found, although I have no ides which ones (or all) are relavent to my warm weather re-start problem...
PO-122 TP Sensor Circuit Short or Low
PO-161 O2 Hearter Bank #2 Sensor #2
PO-171 Fuel System Lean Bank#1
PO-174 Fuel System Lean Bank#2
PO-300 Missfire
PO-410 Air Injection
PO-441 E??? (can't read his writing on this one!)
PO-1415, 1416 Air System Fault Banks #1 and #2
Like I said above, I have had a partial tuneup done, but it has not cleared up the warm weather re-start issue.

ND and le - Thanks for the links!
k

If anyone has a Factory service manual, It would be handy to see how many of those circuits share a common ground point. Might be a bad ground contributing to codes.

TP (TPS) is throttle position sensor

lake - Yeah, we did not replace the TPS (although it could be a contributor to my warm weather re-start issue) when replacing the plugs, wiring, etc....mechanic forgot about that item. With 175,000 miles on a second engine (GM Factory), I am trying to spend what is needed to correct the re-start problem (and some reasonable cost engine issues) and trying to get by with the car for another year. I don't anticipate keeping the car much longer.
k

I have the same problem I think. I have a 92 5.7. when I drive more then a half hour it will stall at lights, so I have to hold the gas and brake at the same time without spinning the wheels, when I park it, it get worst, so waiting to buy a cap and rotor. maybe some plugs too. hope it would help. What i did so far, Checked vacuum good. spark plugs new, fuel filter new. oil change, cleaned fuel injectors. and seafoamed. BTW 205.000miles, What do you guys think?

CarloNYC wrote:

I have the same problem I think. I have a 92 5.7. when I drive more then a half hour it will stall at lights, so I have to hold the gas and brake at the same time without spinning the wheels, when I park it, it get worst, so waiting to buy a cap and rotor. maybe some plugs too. hope it would help. What i did so far, Checked vacuum good. spark plugs new, fuel filter new. oil change, cleaned fuel injectors. and seafoamed. BTW 205.000miles, What do you guys think?

Do you have any engine codes?

First you could also check the ground at the thermostat housing. Only remove the stud when the engine is cold so that water does not seep while it is out. Clean the hole, stud, and the lugs with WD40/PB blaster/CRC, then reassemble. Test run the car. Cheapest

If that does not work, check/replace your PCV valve and test run the car. Cheap.

If that does not work, check/clean you Idle Air Control valve, and test run the car. Can be cheap if just dirty (carb cleaner), more expensive than temp sensor if replaced.

If that does not work, check your temperature sensor on the intake manifold, and test run the car. More expensive.

If that does not work, check/replace the EGR valve and test run the car. Most expensive.

You can also check for vacuum leaks when hot...use a couple drops of dishwashing liquid in a quart of water, and squirt on any place there might be leak.

You should have an FSM for proceedures.

Like Fred said, check codes first. If I recall correctly, code 41 and 42 would be ignition related.


Heat soak issues are usually manifested by starts in the morning, but once you get somewhere, it won't restart. ex: going in the store to shop for a short time, after you come back out .. no start. Maybe a few hours later after everything cools down it will start again. The problem seems to become more pronounced with time, as the more times it gets heat soaked, the less reliable the car becomes.

On stock motors this should be less of an issue than modified ones. Headers in particular raise the under hood temps significantly.


Here's a thread from the Camaro / Firebird website that goes into more lengthy discussion, and my final solution. Haven't had an issue since.

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Makes sense. Its the ICM. I guees they dont last very long with all the heat in the cap. Cost 45 bucks. might as well get the pick up coil. cap- rotor and plug wires. thanks guys,

CarloNYC wrote:

Makes sense. Its the ICM. I guees they dont last very long with all the heat in the cap. Cost 45 bucks. might as well get the pick up coil. cap- rotor and plug wires. thanks guys,

When you install the ICM, if that is the problem, use heat sink compound, not dialectric grease. They are not the same. You can get a tube of the compound at Radio Shack.

I would try one part at a time. If you fix the problem, you can stop throwing money at the car. Start with the cheapest thing first. The ICM is one of the most expensive parts, so do it near last. Do the items in the list I gave you with the cheapest first. Check the wires at the ICM connector before you start messing with the ICM. The internal connector for the ICM from the pickup coil is usually very brittle. I have yet to remove one without breaking it. You can get a cheap pickup coil and swap out the plastic part of the connector, but you will have to remove the distributor to get at it. It is a lot easier to swap the plastic part than replace the coil, which requires the disassembly of the distributor.

I check the ground at the thermostat housing, I did not take the bolt out, just the nut that held the two grounds, cleaned them up with sand paper.

I checked the pcv valve by shaking it? It moves, i guess it works.

I took off the Idle Air Control valve off and cleaned it. it the thing in the back right of the tbi?
I also heard if you tap it when running and notice a jump it idle its going bad. works fine.

I do not know where the temperature sensor is. if its in the front with a plug on it? I do not know how to check it.

I checked the egr valve by adding a hose to it and sucking to see if it moves, moves fine.

No vacuum leaks.

I had the codes read with a genesis computer. he said no codes. but maybe i can use a wire and read it myself.

Funny thing its been good for two days now, but have not drove to far nor to hot out side. in the 70s here. Thanks.

Maybe you have accidentally fixed the problem. I was leaning toward the ground at the thermostat housing.

PCV valve is probably OK.

IAC may have been the problem as well.

I would not second guess the genesis computer, it probably told you the truth.

You should go out and force the issue to see if it is genuinely fixed.

At a stop light the idle jumped up alittle bit but did n t die. I can live with it lol. thanks buddy.

The stud for the thermostat ground may be corroded on the threads. I would check it. It is basically a freebie, but can be really troublesome.

Nice thread hijack,.

Hijack police?

Fred, I will do that . I didnt at first because I did not have a 14 mill long socket handy.

CarloNYC wrote:

Hijack police?

Fred, I will do that . I didnt at first because I did not have a 14 mill long socket handy.

Not really hijack police,. but an lt1 problem hijacked by a tbi problem,.
not so good for kahunna,.
Kahunna,. theres a drain back valve in the fuel pump in the tank,.it could be bad,. (turn the ignition on/off a couple of times with 5 sec pauses) see if that helps,.(loses all residual fuel pressure)
But its likely a dripping injector,. floods the intake over time, takes a while for everything to clear itself,.(try cranking with your throttle held to the floor see if it fires quicker and cleans out sooner)
Mebbe start the car thru the window,.(after its sat for a while) walk to the back while its spluttering at a dead idle, and see if one of the pipes smokes a little (not steaming) that'll give you a clue to which side its on,. (unless you have a balance pipe between exhausts,)

HIGHLY DOUBT it's the opti spark,.but go ahead and listen to the opti dramatists,..its usually the first thing that they with little LT1 knowledge point at,.
a bad tps will give erratic off idle running hot or cold,.

JMHO
YRMV
NWEOI
PDCC

Nick

Carlo's Fred is right about the TBI thermostat housing being a cause for many oddball running
conditions.Its a cheap and quick fix but its easy to screw up.You must get it very CLEAN and
free of rust when putting it back together.Make sure all of your wire ends are clean and dry
when reassembling.
Take Care
Jim Gordon

Flasheroo wrote:

Carlo's Fred is right about the TBI thermostat housing being a cause for many oddball running
conditions.Its a cheap and quick fix but its easy to screw up.You must get it very CLEAN and
free of rust when putting it back together.Make sure all of your wire ends are clean and dry
when reassembling.
Take Care
Jim Gordon

KAHUNNA,...just in case you missed this post amongst all the wealth of info for aTBI car which bounced this thread onto page 2 now,.

Quote :

Not really hijack police,. but an lt1 problem hijacked by a tbi problem,.
not so good for kahunna,.
Kahunna,. theres a drain back valve in the fuel pump in the tank,.it could be bad,. (turn the ignition on/off a couple of times with 5 sec pauses) see if that helps,.(loses all residual fuel pressure)
But its likely a dripping injector,. floods the intake over time, takes a while for everything to clear itself,.(try cranking with your throttle held to the floor see if it fires quicker and cleans out sooner)
Mebbe start the car thru the window,.(after its sat for a while) walk to the back while its spluttering at a dead idle, and see if one of the pipes smokes a little (not steaming) that'll give you a clue to which side its on,. (unless you have a balance pipe between exhausts,)

HIGHLY DOUBT it's the opti spark,.but go ahead and listen to the opti dramatists,..its usually the first thing that they with little LT1 knowledge point at,.
a bad tps will give erratic off idle running hot or cold,.

JMHO
YRMV
NWEOI
PDCC

Nick

Sorry officer Nick!!!!!!!!!!!!!!!!!!!!Keep up the good work I feel safer already.
Jim Gordon

Flasheroo wrote:

Sorry officer Nick!!!!!!!!!!!!!!!!!!!!Keep up the good work I feel safer already.
Jim Gordon

FU

Always the gentlemen Nick,take care!
Jim Gordon

Flasheroo wrote:

Always the gentlemen Nick,take care!
Jim Gordon

You're like my ex-wife,. talk alot, say nothing worthwhile, and always have the last word

Nobody has the last word with you, Nick!
Take Care
Jim Gordon

Nick - Thanks for the clarifications! Will try your suggestions regarding the fuel tank area. Is a leaking injector repair a big (expensive ) job? Have not been on here much the last week or so, because our outisde temps have been cooler (70's) with a lot of cloudy days = no warm weather restart problems! Did have one episode this week in a grocery store parking lot...had driven the car fifteen to twenty minutes (air temps were low 70's) to the store. I came out to the car after forty minutes in the store, and it rough idled on me when it started (had gotten sunny/muggy with temps around 75). I cut the car off and tried it again...this second time it idled a little less rough and I was able to back out of the parking space and head out...where it ran fine. I will be back on the research trail as it warms up...I'm sure I will be having the restart issues again.

I just got done replacing the fuel pressure regulator and the vacum hose that connects to it. Mine was starting to run a bit like yours. I noticed that the elbow on the vacum line that is attached to the manifold had a small hole in it and when I pulled it off, it was a little wet with fuel.

94 LT1 Wagon - What led you to that regulator/hose repair? Was there a gasoline odor under the hood? Were there any codes thrown that took you there? k

changed cap-rotor, plugs wires and ignition mod and runs like new on my tbi. no more stalling when hot.

Feels great when you manage to fix a problem with your own 2 hands.I know I get a lot of
satisfaction when I manage to repair something on my own.Gotta go Carlos before I get
yelled at!
Jim Gordon

Just wanted to finish this thread off...ended up it was the opti spark distributor. Finally gave up on me a week ago on a hundred degree day. Had it repalced (ouch...$900.00) and is running good again. Thanks to Nick for the suggestions...Flasheroo, I'm up the road an hour north on 17 from you in Tappahannock area! k

Thats great to hear Kahunna!Are you planning on making the Mid Atlantic wagon fest?I am going
to pm you my number.It is truly a small world and getting smaller everyday!Glad you found the problem but am very sorry about the cost of getting it fixed!
Jim G