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Poor acceleration

1997 hyndia elantra,this car has very poor acceleration between 1000 and 2000 RPM just like there was no fuel.

We have:

replaced plugs and wires

replaced fuel filter and fuel pump

replaced temp sensor

Occures when the engine reaches operation temp.

Any ideas???

Hmmm…does it have an EGR valve? Does the idle suffer or any other symptom accompany this condition? It’s obviously a closed loop: non-fuel enrichment apparent condition.

I find it odd that you don’t report a CEL. Typically something that would cause this level of performance alteration would also produce a code.

This is a mass airflow engine. I’d probably CAREFULLY (or care-fooly if der (h)Arnold was saying it) clean the MAF sensor. Get the right spray cleaner for the job. They’re expensive if you screw them up.

The EGR valve has been replaced. The idle is steady. There are NO codes displayed (and yes, there should be a fault code for this). I havn’t tried to clean the MAS but I did take it out and took a close look at it, it was very clean.

Clean the MAF anyway - it takes about the same amount of time as looking at it and the little sensor wires are so small that it could well be contaminated no matter how it looks. Presumably the air filter is clean, and not a K&N.

You could be having problems elsewhere in the ignition system - coil pack/distributor/whatever it has. I once had a coil pack that would only misbehave at low speed/throttle & was otherwise fine.

I would also put a meter on the throttle position sensor since 1-2000 rpm may also correspond to similar throttle positions.

When the EGR was replaced were all of the tubes/passages cleaned out really well? Clogs there tend to cause as many or more problems than the valves themselves.

The EGR tubes are clean, I will put a meter on the throttle position sensor to see if it has a smooth reading over it’s entire range. As for the MAF, would carb cleaner work or should I use a different product?

Use only a MAF sensor cleaner on the MAF - although I’m pretty sure that MAF sensor cleaner is just a basic electronics cleaner. Never being completely sure about that I always use the can that say MAF sensor cleaner. MAFs tend to be expensive.

Well, the MAF sensor is cleaned, still the same…When the car is STONE COLD, it runs great, within the first 5 minutes, the acceleration goes all to hell. It must be a sensor that is now Temperature sensitive but I don’t know which one it might be. Any ideas?