Starting Trouble After Running

[WeSki]

In the mornings or after the car has sat for a couple for hours it starts right up and runs fine. At least once a day turning off the engine after driving a few miles it won't start back up if I try to re-start it within 20-30minutes. This is random and I haven't been abel to determine any pattern or cause. After cranking the engine for about 10 seconds the engine maybe fires a couple cyclers then dies. Crank it for another 10 seconds and it will pop over again but won't start. This has been happening so much that I've gotten pretty go at getting the car started after 5 or 6 long crankings. Once I get it started it sputters and shakes then smooths out but at high idle, 1500-2000 RPM. Sometimes the idle will oscillate between 1200 and 1800 RPM after a difficult starting described above. The battery is strong and cranks the engine over easy and fast. Also after a couple 10 second crankings you can smell a lot of fuel fumes and no, I'm not pressing the throttle while trying to start the car. The car runs noticeable better in the morning when it's cold but after running for 15 minutes or so the idle RPM sometimes goes nuts; at a stop the idle may stay at 2000 RPM or oscillate up and down or idle real low to the point of almost stalling. When driving the car it runs with no issues, the trouble only occurs after coming to a stop or sitting down and then re-starting.

I checked for engine codes; None

​Today I did the following:

Replaced the Wire Set, Spark Plugs, Rotor, Cap (the best i could tell these have never been changed)

Changed the Oil, Oil Filter, Air Filter

Cleaned the Throttle Body, IAC, EGR valve

​After completing the above maintenance and cleaning the engine fired right up and ran smooth idling at about 1100 RPM; RPM dropped as the engine warmed up. when the engine reached a good operating temp the idle dropped to about 800 RPM in neutral, about 650 in Drive. The just a few minutes after the engine warmed up it began to oscillate 1200-1800 RPM. I let it oscillate for minutes then shut it down. I should of got out and watched the engine but didn't. I tried re-starting and to go through my routine described above; I got it started after 5 long crankings.

Still no engine codes

All comments welcome.

Prostar

1994 LS400; 145k miles.

[billydpowell]

no answer here, but, I think you have fuel leaking into your cylinders and the plugs are wet and wont fire until the spark dries them off

[Exhaustgases]

With out some good test instruments its kind of a try this or that sort of thing.

Heat related : Here are some could be's. Engine coolant temp sensor, Crank position sensor, igniter, coil, fuel pump resistor. And don't rule out the ECU capacitor issue.

[WeSki]

Thank you both for your input and suggestions.

Today was a good day, after weeks of no starts and erratic idle the car finally gave a check engine light and the TrackOff light.

Here are the Engine codes:

24 Intake air temp. sensor signal

31 Air flow meter signal

71 EGR system malfunction

Trac codes:

48 Sub-throttle position sensor signal is 4.3V or higher, or sub-throttle position sensor signal is 0.2V or lower when idle switch is OFF

51 Problem in engine control system

The 24 & 31 sound like something to do with the MAF but I don't know

I cleaned the EGR valve but didn't test it. The EGR on my 94 LS is electronic controlled, my 92 LS was vacuum controlled. Are there any good instructions on testing the EGR valve and EGR system?

The TPS is easy to get to, again Are there any good instructions on testing the TPS?

Wow, 51, sounds like Lexus engineers didn't know what to do with the random issues and rolled them in to one code. Can you say Punt. I would love to get some direction on this too.

Thanks, your feedback is appreciated.

[Exhaustgases]

With codes like that very likely the ECU capacitor issue.

Though you can have unrelated to the problem codes, but I don't think that many.

Here is some study material for you, see if your problems are the same as listing in this thread.

http://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

[VBdenny]

Before you go all deep with that stuff, maybe try adding a few bottles of Complete Fuel System Cleaner. Very often the IAC (Idle Air Control) valve tends to stick and not properly regulate idle fuel flow forcing an overfuel issue which could cause your problem. What the IAC does is controls the extra fuel which is added during cold starts (about exactly the same thing a choke did on a carburetor prior to fuel injection). When this valve sticks OPEN, the fuel flow when engine is cold is about right and the car should run fine. However, as the engine warms and if this valve does not close, then extra fuel is being dumped into your combustion chamber even when it isn't needed which causes the fuel smell and stalling. ALL of these codes can certainly be related to this issue so it is well advised to check out the cheapest things that could be wrong before getting into the expensive stuff. Just because an O2 or other sensor is on does not mean that it is broken, rather just doing it's job when it sees things out of skew.

This problem is much more prevalent on engines in which people use economy gasoline as those fuels often do not have the additives found in Top Tier fuels.

Hope this offers some insight.

Denny

[Exhaustgases]

And how did you clean the throttle body? Did you spray anything into the air meter? If so you likely ruined the air meter as there is no way to clean it, unless maybe take the unit apart, it is a sealed unit. I'm not sure where the intake air temp sensor is maybe a spray product would goof it up too. The egr maybe you did something wrong with it and why its throwing the code.