Churchkey

90 injectors are problematic ohm test them, cold engine 14 - 16 ohms.

Purchased Bosch 111's from Jon @ FIC here on the forum for my 90.

aklim

I wouldn't waste more money on the snake oils to clean the injectors. To remove any bias, I would take the hose off the FPR and cap the nipple to the manifold. That gives atmospheric pressure and max fuel pressure. Lets see if it keeps supplying fuel pressure at idle and then WOT and how long it holds pressure after shut down and go from there.

How is your spark? Lets do this at night. Make sure you have a new plug gapped. Do each cylinder and see if you have a blue flame. Sure, it will run rough on 7 instead of 8 but WGAS?

Also scan for the engine temp and do an infra red thermometer on the ECT (not the gauge) sensor. That way, if the ECM sees 120 and the thermometer says 180, you have a problem.

As to your injectors, they are definitely dirty and/or Multec. For what you get reman ones for from FIC, you probably would be better off changing them. While they are out, you can take the TB off, do a coolant bypass, take the top plate, IAC and IAC housing off and clean the passages. Reinstall with new gaskets. DO NOT PUSH THE IAC PINTLE. Spray with brake cleaner and wipe GENTLY.

aklim

Does Rock Auto sell it as a kit with all the "fixings"? Also, do they eliminate the pulsator?

Tom400CFI

That was even posted in post #2.

Klondike

Just changed my fuel pump a few months ago. One of the easiest fixes on a C4. Easy to siphon gas out of a C4 but not really necessary for a pump change.
The new fuel pumps are a turbine style that do not require the pulsator and just include a piece of fuel rated hose to replace the length where the pulsator is removed from. The older style pumps were a gear-rotor style that delivered the fuel in little pulses as each gear came around and needed the pulsator as a "shock absorber" to smooth out the flow to the injectors. The new turbine pumps are smooth delivery and don't require that extra damping.

aklim

Why? Run it till it is empty so you have less to mess with. All my cars run till the tank is empty before filling. Might have to dump a gallon or two to make it home but you have now got an empty tank. If you don't believe that it is empty, toss a lit match.

Good information. I actually prefer the Ractronix kit for ease of assembly. It comes with the gasket and new SS hex head bolts. For $30, it is worth it. No trips to the store.

Tom400CFI

Guys, you don't need to empty the tank at all in order to change the pump.
Just pull it out, stick the new one in.

But first, diagnose that it needs a pump.

pologreen1

Timing and or fuel.

Fuel filter, injectors, TB, timing. Possible computer issue since its a '90.

Did it run fine before?

Bad gas is NOT the issue. My car sat 10 years until 2 years ago with the same gas and no additives. I have never used additives. never had an issue.

aklim

Why? It's so easy. Open tank up, drop lit match, no more fuel. Tank empty.

And take the fun out of it? Nah. Why, I'll bet it is because the PO ran the car low with less than a quarter tank that caused the pump to burn.

Seriously, you are correct. We don't even know if fuel delivery is a problem.

aklim

Just because of age or were the computers a weak spot?

pologreen1

'The year IMO but mine had a similar issue 2 years ago. Only it would eventually even die at 5,000rpms. Several of the top tuners and tune writers here and other more sophisticated forums for FI tried to fix it and could not.

I'd say a very small chance it's that and totally and completely last place to check.

We don't know if some weekend pit crew guy with a tuner was in his car's system either trying to play tuner.

http://repairpal.com/engine-control-...m-can-fail-350

keet

Ok, checked the fuel pressure, 38 psi. Checked the vacuum, 18 psi. Still the same, starts fine, revs fine the first press of the gas, the next press of the gas, it stumbles and pops, and if you hold the gas pedal down it'll bog and just about stall.

Nokones

The fuel pressure at 38 is a tad on the low side. You should connect a fuel pressure gauge and tape it to the windshield and drive the car and check the pressure under load. If the pressure drops you could have either a regulator or a pump problem.

aklim

I'm not sure what the vacuum has to do with this test. You turn it on and it jumps up before cranking. After that, the next thing we need to see is whether it holds pressure.

keet

low??? Service manual says 34-39.

keet

We tested the vacuum as well, just throwing that information out there.

keet

yes, it held pressure

keet

Haha, yes, there was blood all over the one header by the time i was done!

Tom400CFI

^THIS^.

Pump may very well meet the requirements at idle. Your symptom is not occurring at idle, however.

keet

I didn't drive it around but i did press the accelerator (while in park, in my driveway) and the pressure stayed pretty even.