Just bought a 91, RS, 6 cyl, MPFI, 80k miles. My daughter's first car. Car always rough when first started, engine smooth once warmed. Now that temps dipped below 40, engine will not start. Turns over, and coughs like it wants to start, but just won't. I charged the battery, cranks fine, but won't start.

Is there a sensor that acts as a choke for fuel injected engines? what else can I look at?

 

Oh, boy, there is so much it could be. Yes, there is some sort of "choke" feature, but frankly I can't remember if it is mechanical (a butterfly) or eletrical (software, solenoids) on the '92. Given you say it is multi port FI, its probably electric.

The only clue you have (or at least gave here) is the rough running when cold. Things you could try, which I would give only a 40% chance of working are: change the air filter, fuel filter, and clean and gap the plugs, check the wires. If that stuff is marginal it would start and run in warm weather but not cold. It could be this but likely not: regardless its stuff that should be taken care of so it won't hurt to do it.

On a car nearing 15 years of age, is equally likely (another 40%) to be the fuel delivery - fuel injection jets dirty or worn. They aren't cheap to replace so only do it if you know. You would have to have this checked, although you could run some cleaner through it if you know how (you have to get the car started first, however, which probably means waiting for warmer weather) but only a shop with knowledgeable techs can run it through in the best way.

REgardless, those two 40%s add up to 80%, which leaves a 20% chance it is something with the "choke" or cold idle richness control. There, I can't advise you beyond it would need a shop to look at the MPFI.

 

Thanks for the reply. I checked & cleaned plugs, wires seem good. What about the Manifold Air Temp sensor? any thoughts on that?

 

It could be nearly anything on a car 15 years old - you just don't know who and what, but I think it would either give you a check engine light, or go ahead a start even if poorly, if that were it. Of course I could be wrong. good luck.

 

Some things you can check:

If check engine lite is lit while it is running, scan car & see what it is complaining about. The lite should come on and go off right after turning ignition on, this indicates computer is gettin power.
Check plugs & see that they are firing clean, not fouled or wet with fuel.
Check fuel pressure at fuel rail test valve with a fuel injection pressure gauge. Should be around 40lb with ignition on & engine stopped.
If no pressure, the fuel pump is not running. Check fuse, pump relay, fuel pump dead.
Check Intake Air temp sensor. If it lies to the PCM & gives wrong temp, it will make it hard to start engine
EGR valve should be closed at engine start, otherwise mixture will be too lean
Check MAP sensor, nothing works if it is dead
Check IAC valve. should be clean and pluger able to move freely against spring
Get a set of NOID lites & check that all injectors are being fired
Check all vacuum hoses for leaks
Check TPS with ohm meter, Disconnect electrical connections first
Make sure battery is fully charged

Note : PCM double fires injectors during start to richen mixture

If u don't have one get a FSM or a Haynes Service manual.

Pete

 

take it to a shop or a school auto shop. They can put it on the sun machines and identify the problem. We did this in my autoshop class on my teachers 92 camaro and made it run right. There is too much complication with all of the computers unless you know what your doing.