Does coolant temp sensor actually control the FPR vsv?

[David8a]

Ive been having some idling issues on my 94, it stumbles and ive already replaced the MAF, IAC, FPR, and fuel pump. Ive tested the fuel pressure on the fuel rail and everything was within spec. One thing I noticed was that the fuel pressure regulator has vacuum going to it when the engine is cold and hot. Is that normal? Because when its cold and I remove the vacuum line from the FPR, it idles normal. I read that a coolant temperature sensor controls the vsv for the FPR, wondering if anyone has had any issues like this before

 

[petegangies]

Ive been having some idling issues on my 94, it stumbles and ive already replaced the MAF, IAC, FPR, and fuel pump. Ive tested the fuel pressure on the fuel rail and everything was within spec. One thing I noticed was that the fuel pressure regulator has vacuum going to it when the engine is cold and hot. Is that normal? Because when its cold and I remove the vacuum line from the FPR, it idles normal. I read that a coolant temperature sensor controls the vsv for the FPR, wondering if anyone has had any issues like this before

have you messed around with your tps? I assume you've checked your timing in diagnostic mode? checked for codes? oxygen sensor? any recent work completed on the vehicle?

Absolutely normal for the FPR to have vacuum.

 

[David8a]

have you messed around with your tps? I assume you've checked your timing in diagnostic mode? checked for codes? oxygen sensor? any recent work completed on the vehicle?

Absolutely normal for the FPR to have vacuum.

There are no codes, the o2 sensors are about 2 years old, haven't done any recent work on it, just took it on a short road trip and it started to do that out of nowhere. I haven't messed around with the tps nor I haven't checked the timing.

 

[Malleus]

You have found one of the hidden "golden screws" in the 80 series. That little VSV can and will cause problems if it's not preforming properly.

 

[petegangies]

Mine had a stumbling idle, and it was a combination of the oxygen sensor, and the connector to the oxygen sensor (my 94 Australian delivered model only has one). Have you driven through any water, puddles etc? Have you checked thoroughly for vacuum leaks?

 

[David8a]

Mine had a stumbling idle, and it was a combination of the oxygen sensor, and the connector to the oxygen sensor (my 94 Australian delivered model only has one). Have you driven through any water, puddles etc? Have you checked thoroughly for vacuum leaks?

I haven't driven through anything but dry pavement recently. Ive checked thoroughly on every vacuum line.

 

[petegangies]

how bad of a stumble are we talking? Have you removed the vacuum line to your fuel pressure regulator and checked for fuel residue? It should be 100% dry.

 

[David8a]

how bad of a stumble are we talking? Have you removed the vacuum line to your fuel pressure regulator and checked for fuel residue? It should be 100% dry.

It bounces between 550-700 rpm. I noticed that I hear a click and it becomes steady. Sometimes when I put it in drive and go, it hesitates untill I repeatedly press the pedal then it goes. Sometimes it doesnt do that and it acts normal like nothing is wrong. Ive removed the vacuum like and its 100% dry.

 

[petegangies]

yes, mine would make that noise and suddenly idle fine. Check your EFI fuse is not warped/melted. Check the connectors to your o2 sensors are okay, and inspect the wiring near your EGR (you may need to unwrap sheilding to inspect properly).

 

[David8a]

yes, mine would make that noise and suddenly idle fine. Check your EFI fuse is not warped/melted. Check the connectors to your o2 sensors are okay, and inspect the wiring near your EGR (you may need to unwrap sheilding to inspect properly).

I will look into those this week.