Help! 87 L98 rough idle and surging

[keither]

My 87 convertible was running great until a week ago, now it idles rough and varies between 500-900 RPM at idle, and surges or misses at light throttle when cruising.

I cleaned the MAF with the proper spray cleaner, and the throttle body too with little or no improvement.

I added Chevron Techron Plus at the last fill-up, no help with this problem.

I'm chasing vacuum leaks, and have fixed a few with no solution yet.

There are NO check engine codes,
even though I have made a few modifications such as, K&N air filter, air pump eliminator kit, disabled the EGR by plugging its vacuum line. I also added a chambered dual exhaust system with a new Bosch O-2 sensor that is too loud but I like it.

The car has been running great with those mods until this week, and it seems to get worse when it warms up, but it's never run over 185 degrees any way.

What should I try next?

Thanks!:confused

 

[formul8]

Could be Vacuum leak, fuel pump, fuel injectors.

 

[sstearns2]

My 87 convertible was running great until a week ago, now it idles rough and varies between 500-900 RPM at idle, and surges or misses at light throttle when cruising.

I cleaned the MAF with the proper spray cleaner, and the throttle body too with little or no improvement.

I added Chevron Techron Plus at the last fill-up, no help with this problem.

I'm chasing vacuum leaks, and have fixed a few with no solution yet.

There are NO check engine codes,
even though I have made a few modifications such as, K&N air filter, air pump eliminator kit, disabled the EGR by plugging its vacuum line. I also added a chambered dual exhaust system with a new Bosch O-2 sensor that is too loud but I like it.

The car has been running great with those mods until this week, and it seems to get worse when it warms up, but it's never run over 185 degrees any way.

What should I try next?

Thanks!:confused

I had this problem on my 89 years ago. It turned out to be the MAF burnoff relay. There are two relays on the firewall behind the battery if it's the same as an 89. Try replacing both, they're cheap.

Scott

 

[JAKE]

The 86 I use to own had those symptoms on a few occasions.

First time it was a broken MAF wire,

The second time was a dead 02 sensor and

Last time was a vacuum leak at the #1 injector (where it fits into the intake manifold).

Jake

 

[keither]

Could be Vacuum leak, fuel pump, fuel injectors.

Thanks I will check them out.

 

[keither]

The 86 I use to own had those symptoms on a few occasions.

First time it was a broken MAF wire,

The second time was a dead 02 sensor and

Last time was a vacuum leak at the #1 injector (where it fits into the intake manifold).

Jake

Thanks Jake, Which MAFwire? the connector or the tiny wire inside?

 

[keither]

I had this problem on my 89 years ago. It turned out to be the MAF burnoff relay. There are two relays on the firewall behind the battery if it's the same as an 89. Try replacing both, they're cheap.

Scott

Thanks Scott,
I will replace both relays, good idea, saves me some troubleshooting time;
Keither