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Saturn SL2 1999 - Code and intermittent starting problems

Hello, Everyone.
Talked to 4 reputable mechanics, no help, problem persists. Here are the facts: a few months ago, the check engine light came on. This code came up: “P0506 - idle air control revolutions, permanent lower than expected” but beyond scope of oil change shop I was at so I immediately drove to a mechanic.

Mechanic 1: Code did not come up again at mechanic’s shop, check engine light was off, and mechanic said there was nothing to do at that point.

Mechanic 2: Later, a mechanic on the phone told me the code could mean the following: a leak, idle control valve is bad, dirty tustle(?) body (not sure if that’s correct - my handwriting is pretty bad on the notes I took), or poor electrical connection.

Current symptoms: A few weeks later after a short stop, car would not start: it would start to crank but would not turn over. When it did turn over after the third or fourth try, it was idling very low, and stalled out when I put it in gear. I waited 20 minutes, restarted with the very same issues repeating. Check engine light has not come back on at all.

Mechanic 3: Took it to a mechanic who said if the problem was not occurring at the moment, there is nothing he can do. He changed the spark plugs.

Symptoms persisted: A couple of weeks later: trouble starting after a short stop, stalled when put in gear, waited a while and then it started up fine. When driving, it seems to be idling lower than usual and feels as if it is about to stall, but has not (yet).

Mechanic 4: Mechanic said the code is meaningless and that if the car is not replicating the problem at the time they are in possession of the car, they can’t diagnose the problem. So I told them to keep the car all day to run their errands. The problem occurred for a just a moment just like I said for them (after a short stop) but that it started up again shortly thereafter so they could not diagnose the problem.

Mechanic 4 said the idle is too low at times but felt it was also too high at other times. They did not actually look at anything under the hood, just connected gauges. Other hypotheses that were proposed by the shop: a fuel pump problem (but can’t tell me whether that is or is not a problem - numbers read fine on gauges while car in their possession), or a thermostat problem. The shop is going with the thermostat problem but my confidence is low since learning they never checked the idle control valve or looked for gunk, just connected gauges to read current numbers on an intermittent problem. The computer code does not show in the history, according to current mechanics, but they insist there is nothing wrong with computer because “there can’t be”.

Rationale: for problem being with the thermostat given by the mechanic (not sensor): he drove about in 100 degree heat, said he used the car during the day and parked it in the sun, and the temp. gauge shown to the driver in the cab should read closer to the middle temp, and it was reading at halfway between cold and the middle temp. At garage, 184 degrees and he thinks it should have been well over 200 degrees.

My questions: 1) why won’t anyone check the idle control valve or look under the hood for gunk in potentially problematic places? 2) are those codes really meaningless? and 3) what are possible problems and why do you think so? Thanks so much :slight_smile:

Just one thing…maybe two. Please break down your “Gone With The Wind” post into paragraphs. It makes it easier to comprehend. The other thing is…you need to feel very lucky that you only got one CEL code since you felt compelled to go to Iffy Lube.

Please find a good independent mechanic that will assess your problem based on the code. You won’t find any mechanics at any quickie oil change places and at any of the myriad of tire shops or places like them. Yes…the codes are meaningless to someone other than a mechanic with experience. Break that post into paragraphs and you may get more answers to your questions. This is the best that I can do at the moment considering the fact that my head is spinning right now.

@missleman: I did in fact go to 3 actual mechanics,not 3 Jiffy Lubes, and gave them all the code and none could do anything with it, they said, if the problem was not replicating in the moment. I am sorry that the post is too long for you. Thank you anyway for trying.

No problem @KuriousKat … some faults can be tough to solve. Since the IAC is mentioned in the code and they are relatively inexpensive and easy to replace…just install a new Idle Air Control. I think they run about $30 at most auto parts. It could save you some money and I think it’s worth replacing in any event. It’s no guarantee of a fix but I do guarantee that you will have a brand new IAC.

@missleman: thank you, and I did take your suggestion to break down the post into paragraphs and to shorten as much as I could without losing pertinent information. Now, I if I can get someone to agree to change out the IAC -I don’t understand why they are not considering that a logical approach given the code that came up.

@KuriousKat …I don’t either but I’ve been very successful maintaining a logical approach so I stick with it when dealing with vehicles.

Don’t replace the IAC just yet. Do you have the single cam (8 valve) engine? It is the most common engine in Saturn’s. If so, then I think you had a previous issue with a high idle but you may not have noticed it.

The code P0506 is for low idle speed. The biggest issue with the Saturn SOHC engine is the intake manifold gasket around the #1 intake port. The #1 port only has three bolts around it, and since it is a square port, that means one corner, the upper outboard corner is missing the bolt. In addition, there is no support bridge between the #1 and #2 ports.

The factory gasket was a flexible fabric gasket and it would get sucked in to the port where the bolt is missing. When the leak is small, it throws off the MAP sensor located at this end of the manifold and causes the idle to rise. As the leak gets worse, it degrades into the conditions you have now.

It is easy to confirm. You or your mechanic can spray something like WD40, starter fluid, carb cleaner etc, whatever is lying around the shop that has some volatility. If the idle changes in any way, up, down or the engine dies, then there is a leak there and the gasket needs to be changed.

If this is the case, do NOT use another factory gasket, get a felpro gasket instead. The felpro gasket is foil backed and a little stiffer. Even though it is generally frowned upon, I’d also suggest that a gasket adhesive like copper coat be used on the manifold side of the gasket to help keep in it place. I did that on mine after going through two factory gaskets and never had another problem.

BTW, if your mechanic is hesitant about using a sealant between two aluminum surfaces, the factory gasket does have a bead of copper RTV built into the gasket in a bust plastic bead. The plastic bursts as the manifold is torqued down to spread the sealant, but it doesn’t work. Not adhesive enough.

BTW, replacing the gasket is about a $200 job. If you want to try something on the cheap, you could try to seal the gap between the manifold and the head at this point by pressing some RTV into the gap between the two bolts around the section where the bolt is missing. You have to remove the power steering pump to gain access.

One more thing, the thermostat is good. Normal operating temp is 180 and if it does not reach that temp in the prescribed time, it sets another code. I just noticed in your first post that the idle was sometimes high so I am more convinced that its the gasket, but one other issue this engine is known for is the ECTS.

Engine Coolant Temperature Sensor. Some Saturn’s got a plastic tipped sensor that was prone to cracking and causing starting and idle issues, but I don’t really think this is your case. If the ECTS ever becomes a problem. make sure you get the brass tipped replacement, but again, I’m pretty confident that it is the gasket. The gasket is easy enough to check anyway.

Your temp gauge should be two needle widths above the quarter mark when warmed up. It can safely go to the 3/4 mark, but I would try not to let it go over the half way mark.

@keith: thanks for the detailed response! I will run your ideas past the mechanic. Thanks for the help!

I have no idea why a thermostat would cause your problem. I would think a vacuum leak, as suggested, or IAC valve are likely causes.

are todays mechanics helpless without a code to tell them what is wrong?

Hi, Everyone. Just a brief follow up: found a mechanic willing to check out the manifold gasket, the thermostat, and the IAC. He was able to confirm that the idle was erratic - sometimes idling too fast and at other times too slow. Nothing wrong with the thermostat or the sensor, the manifold gasket was in place, so replaced the IAC valve and voila! I haven’t had a problem in 3 weeks. I do believe it’s fixed!

Thanks again @missileman and @keith!

Thanks for the feedback @KuriousKat because it will help others with similar problems. Those IAC valves are common and they do go bad quite frequently. I don’t even bother cleaning them anymore.