86 port FI, open loop (cold) runs great, hot closed loop, some kinda of limp mode, check engine lite on, Coded egr. replaced EGR, reset computer, pulled ground, same experience, good cold, Hot 1500 RPM max, surges, sounds like vacume leak, check engine on, recheck code, lean exhaust, replace oxygen sensor. reset computer restart with same results.

replace the vaccum operated electrically controlled egr assesembly. is my first weird guess other than regular maintnance

I’m happy to assist further over the phone at https://www.6ya.com/expert/christpher_f760d0f18f8eedc3

Does the car have any check engine codes? Usually if the car runs poorly when warmed up, its because the computer tries to put the car into "closed loop mode" when it's up to operating temp but something is wrong. When engine is cold, the ECU uses the coolant temp sensor to adjust fuel mixture, when warm, it switches to O2 sensor and monitors other systems like EGR, etc. In my experience I've seen this be anything from O2 sensor, coolant temp sensor, or EGR valve. Could be a dirty throttle body too, as this is a common issue on the ABA engine.

hot engine
cold
or both
in drive, or park, is this a stick shift car, i dont know.

this is called surging idle. and all EFI love to do that at a drop of hat.
ALL
the hot idle is 800 rpm
bad idle surgine is caused by.
1: EGR leaking.
2: lean combustion for any of many reasons, is EFI holding closed loop status at hot idle, (no , fix that first.
3: ISC is out of control (ISC electric is the ECUs idle controller)
the ISC goes out of control easy.
EG:
a: egr LEAKS.
B. AIR LEAKS.anywhere in the induction path (AIR path)
illegal leaks, MAF engines go lean, MAP engines just race fast.

4: ISC is stuck (clean it)

with all cars. we:
1: check all fuses
2: check the CEL is it glowing running,? yes, then scan it now.
3: check with scan tool for closed loop hot. if fail fix that first.

and lots more..... but i stop here.

Friend, you have a faulty temperature sending unit. Change THAT and you'll have this problem no longer. The temp sending unit, when cold, will put the engine, by the computer, into cold start mode, the engine starts getting a bit more fuel until is warmed up, then the sending unit tells the computer it's warmed up and shuts down the cold start mode. Only makes sense, Right?

The EGR valve is fully closed when cold and opens when the engine warms up to normal operating temprature. Check the EGR valve to see if its closed when the engine is cold. If opened replace it

The EGR (exhaust gas recirculation) valve

What is it? This is a device that reduces engine emissions of nitric oxides by allowing a measured amount of exhaust gas to re-enter the intake manifold and mix with the air prior to entering the cylinders. The EGR can be vacuum or electrically driven or a combination of both.

Where is it located? The EGR is most often associated with the intake manifold. The EGR will be sited at a point of contact with both the exhaust and intake manifolds. If the exhaust manifold is remote, for example on the other side of the engine to the intake manifold, there will often be an exhaust feed pipe leading from the exhaust manifold to the EGR sited on the intake manifold.

How does it work? Generally intake manifold vacuum acting on a diaphragm draws up on a valve to open a connection between an entry port from the exhaust gases and an exit port to the intake manifold. An open EGR port makes starting difficult so the valve operation is often impeded by an electrical over-ride until the engine has warmed up, as signaled to the ECU by the coolant temperature sender. In some cases, a differential pressure feedback exhaust (DPFE) sensor fed by pipes from the exhaust feed to the EGR informs the ECU when and by how much the EGR should be open.

Symptoms of faulty EGR

The EGR has two possible fault modes either it is a) open when it should be closed or b) closed when it should be open. (some EGR faults are in fact more likely to be DPFE related)

• Poor idling: ‘hunts’ at idle and generally rough engine performance. This is due to the air ingress through the split diaphragm or the EGR valve being left open, either event compromises the intake manifold vacuum and in turn this interferes with the ECU’s ability to deliver accurate fuel to air ratio for a given engine speed.
• Misfire and ‘pinking’: if the EGR is jammed closed or the exhaust feed pipe is blocked (e.g. gummed up with baked carbon) the engine ignition runs lean and very hot, so hot in fact that the fuel air mix can spontaneously ignite causing a misfire. The misfire if pronounced can, in turn, be detected by the engine knock sensors and this gives the appropriate on board diagnostic error codes along with the check engine light. Due to the diesel engines creating more soot in the exhaust a blocked EGR is a much more common complaint in diesels than petrol cars.
• Surging: A sticking EGR valve can lead to an effect of rhythmic surging a bit like the MAF fault, especially in turbo charged engines. Normally on a warmed up engine the vacuum from the inlet manifold opens the EGR. If the EGR fails to open promptly the turbo can be subject to a slight boost. Extra fuel/air mix is pushed into the inlet manifold as a result, increasing pressure (decreasing the vacuum). Without vacuum in the inlet manifold the EGR closes again but if sticky does so only slowly. This may allow inlet gases to flow through the EGR into the exhaust manifold for a split second. There is a time lag in the sequence of these events leading the engine to surge in cyclical manner.

How to check? With the engine running it may be possible to force the EGR valve open by pressing on the diaphragm with one’s fingers. Failing that pulling off the vacuum line to the EGR, blocking the pipe on the inlet manifold and applying vacuum to the EGR to monitor function will determine if the diaphragm is split. Removal of the EGR assembly and examination of the ports and valve mechanism will reveal any carbon build up.

How to fix? If the diaphragm is split then the EGR needs to be replaced. Most EGR problems are linked to carbon soot build up and this can be cleaned using a cloth, brush and carburetor choke cleaner spray. If the exhaust feeder pipe is blocked this can be cleaned using a piece of frayed hand brake cable as an internal brush. This makeshift brush can be further enhanced by mounting it in a drill to sweep dirt from the interior of lengths of pipe. Some cars (Hondas are a good example) have an elaborate passage way system to provide exhaust gas to each inlet pipe runner. The only way to clean these out is by removing the blanking plugs (no easy task) and then using the makeshift rotary wire brush and carburetor choke spray. New blanking plugs have to be reinstated to make good the passage ways assembly.

I agree, replace the Coolant temp sensor, it will have 2 wires going to it, Not 1. Usually located just behind the breather near the thermostat outlet.

This sensor controlles your timing and fuel to air ratio.

I too replaced the egr valve and was discouraged that the check engine light came back on with the same "insufficient flow" code. I took it to my mechanic to put it on the monster diagnostic machine. It said "check all vacuum line, and or map sensor". After looking real close we found a melted vacuum tube, and a cracked vacuum angle connector. Replaced both vacuum pieces, reset the codes, and good to go. If that fails than the next thing is the map sensor, that tells the EGR valve what to do.

CHECK THE STATUS OF THE AIR FLOW SENSOR AND THROTTLE POSITION SENSOR