When I give my 88 N/A a quick "jab" of the throttle at idle (with the engine warmed up of course) the RPM's drop to about 500 and the engine stumbles, but recovers and idles normally again. I did a search and couldn't really find anything. Could it be my TPS?

Thanks,
Jeff

 

Could be TPS but more likely to be a vacuum leak I should have thought.
Other typical culprets are insufficient fuel pressure ( FPR etc) faulty AFM or problem with one or more injectors (partially blocked etc)

 

Alrighty, thanks! I'll check those out. Replacing vacuum lines and inspect the AFM for grooves in the contact strip are the next two things on my restoration list. I think read that there's a member on here that everyone sends their fuel injectors to for service. Who might this member be? Or am I thinking of another forum?

 

don't forget the vacuum system is much much more than just the vacuum lines and connectors it also includes the dipstick, oil filla cap, injectors , brake servo hose etc etc

 

I'll recommend what I did after a lot of research. Get a 2" pvc cap and screw in an air fitting. Apply 7 to 10 psi air pressure and spray soapy water solution over everything, incuding the Throttle body, the fittings under the J boot and the intake manifold. Also there's an air cannister next to the battery under the plastic shield below the windshield. After you've exhausted all the leaks, if it still doesn't get better, check the TPS setting (you should hear a click when the throttle open about 1 degree) and make sure the connector is clean and contacts aren't bent. The AFM should be pulled and the barn door cleaned with carb cleaner and using light finger pressure make sure the door doesn't stick. See the Clarks garage item about bending the wiper arm to use a different part of the track. As far as injector rebuilds, use Witch Hunter in Washington state. Bellingham, I think. He charged me $100 turned around in about a week. Top marks for his work. Here's a pic of the PVC fitting:

 

thats not a bad solution especially the air intake blocking and test point but it cannot possibly test or spray all round every connection and joint some of which are out of reach and out of sight.

Much more thorough to inject smoke if you can, because you can see exactly where the leaks are Most owners don't realise that the vacuum system is a lot more than just the plastic lines and rubber connectors
There is a youtube vid on using smoke for finding vacuum leaks which is very impressive

 

How is the dip stick and oil filler cap part of the vacuum system? I thought it was just a plastic tube/plastic cap?

 

have a look at the vacuum shematic in your workshop manual

the dip stick and filla cap are parts of the crankcase pressure system and connected to the intake vacuum system through the ERG and leaks can therefore effect the air flow sensor reading giving false data to the ECU . With some high performance cars you can actually hear the idle note change when you remove the filla cap. Most of our cars are so old now that they all have vacuum leaks to some extent .

 

I see. Alrighty then, well I'll get cracking on fixing my problem! Thanks again!