S13 Idle and running issue

[imm200sx]

Hi Guys,

I have a standard 93 S13 CA18DET, the problem is a rough erratic idle when warming/warm and during high speed work the engine will drop revs and has to be 'coaxed' to raise them again, will cruise at 55-60 but when accelerating hard it kind of bogs down. When the car is stone cold (overnight say) it idles fine for longer but then just goes erratic and lumpy, if left for a few hours afterunning still idles rough. Starts ok all the time.

Things I have tried are:
Hot start solenoid
New fuel pump
Ignition coils and loom
Spark plugs
Dropping resistor
Ignition amplifier
Worst when lambda disconnected
Breather hoses ok
Fuel filter relatively new
Air filter ok
MAF clean

What do people thing next? Temperature sensor? I noticed today seems to be running rich as exhaust pipes sooty (has a cat so pipes should be relatively clean?).

Any ideas? Try the temperature sensor?

[skyshack]

Check the ACC valve and rest of idle air assy.

Wiggle the AFM connector, if revs change its not making good contact.

[Nize]

Yeah as Skyshack has said try those things 1st, and then if no joy unplug the temp sensor (2 pin one) and try it... If the temp sensor fails it usually runs really lean tho, but I suppose anything's possible depending on how they fail internally.

[Nize]

Could possibly be retarded timing too - If all else fails maybe worth checking the belt and the cam and crank marks all line up ok, and if poss get a timing light on it and see what it's like.

[Jonny Wilkinson]

I'd swap out the ETS. They're not that expensive from a factor £10-15.

Also, check the wiring to the fuel pump.

Did you do anything to induce this poor running (or changed anything on the car) or has it developed slowly over time ?

[infamousdirt]

It may be a intake manifold gasket. Its sucking in more air then the car is reading. One thing to try is loosen to intake and crack it open just a bit to let the pressure out from the turbo that is being pushed into the intake. Basically letting air out before it gets to the block so it will equal what is actually going into the block if their were a gasket leak. Just a way to check if its the intake manifold gasket. I just went through this problem, it got worse and worse as I drove it because the gasket just kept getting torn apart and it wouldn't idle anymore, but worked if I kept on the throttle. If you didn't understand what I tried explaining, I can do it in detail if necessary with pictures and what not.

[imm200sx]

Hi, that sounds like really useful information. Do you mean loosen the elephant trunk a crack just before entry into the intake manifold?

[infamousdirt]

Yeah so I had a plug in my intake where a BOV would go, but just a plug, and I removed that which relieved the pressure from the turbo, so it basically created a boost leak before going into the manifold, which made it even out with the leak going into the block. So anywhere you can let the pressure from the intake/turbo so loosen the intake and bend it open just a tad or remove a plug anywhere between the turbo to the intake manifold. Its seems your problem wasn't as bad as mine, as mine wouldn't idle at all so I had to let a lot of pressure out. If yours isn't too bad you don't want to let too much air out before it gets to the manifold or its just going to kill the engine.

I'm not too experienced or anything but this is what I just went through a couple weeks ago so this is my only thought.

[Jonny Wilkinson]

Leaking inlet Mani will let air in at idle and out on boost so high idle and rich running. Its a pig of a job to do especially if its not the problem

sent from t'internet

[s13silvia]

Intake leaks are real easy to find, spray carb cleaner or engine start around the intake side when engine cold. The revs will rise if theres a leak, use the spray to find where the leak is then replace parts.

[imm200sx]

Hi, ok, I did change the temp sensor - no difference. Taking of the intake pipe to the inlet manifold (unmetered air) increased the revs and made the running smoother. Spraying some cleaner around the intake did raise the revs/smooth out the idle so I guess that suggests an inlet manifold leak........

[imm200sx]

PS any hints on inlet manifold removal?

[imm200sx]

Jonny, your description of the symptoms pretty much sum up what appears to be happening...

[s13silvia]

Use a straw on the can of cleaner to determine exactly where its leaking, it could be a loose vacuum hose.It could even be a loose bolt on the intake manifold.

[spanair]

Could possibly be retarded timing too - If all else fails maybe worth checking the belt and the cam and crank marks all line up ok, and if poss get a timing light on it and see what it's like.

This was the case with mines, used to run like a sac of poo due to it being a tooth out and the timing on the cas was maxed out..