MDZ28

So I just finished a thread fixing my AC issues and then this happens....

So here's what happened:

I was cruising on the highway for about 30mins and was trying to merge onto another road. While merging I noticed my car hesitated and barely had power.

So I pulled over and checked all the gauges; they all looked fine.

While at idle the rpms dropped to 500 and then to about 300. It almost stalled so I gave it gas. When I gave it gas it vibrated really roughly and finally returned to 900rpms. If I don't give it gas it will stall.

I checked my oil and my coolant (they were fine). I also checked my mass air flow sensor and it wasn't clogged. Nothing is leaking under the car.

After not finding anything and letting the car cool off a bit I tried to drive it again and there is absolutely no power and it is almost feeling like there isn't any gas in the car (I literally just filled the car up).

Anyways I left the car at a relatives house and had to get a ride home. Hate not parking my baby in my own garage but.....

My question is what should I do next?


I'm thinking its the fuel pump but I'm still not 100%.

Injuneer

Check the fuel pressure - that will tell you if it's the fuel pump.

Scan it for codes.

Run a data log.

https://www.camaroz28.com/forums/com...95-lt1-874306/

HardcoreRM125

Check engine light?

We got to know if:

A - You have any codes pending or history
B - You have fuel pressure over 45? PSI at idle
C - Your O2 Sensors fluctuate between 100-900mV rapidly on a data streaming scan tool.

If all proves inconclusive - I would be looking maybe for a vacuum leak. Spray around all intake gaskets/seals PAST the MAF Sensor with starting fluid with the engine running. If you have a vacuum leak - it will change RPM's.

HardcoreRM125

Also, you could have a Idle Air Control valve issue. If it located in the throttle body and is basically a valve that is controlled by an electronic servo that opens and closes it to control idle RPM on the engine. The set screw on the throttle body is a "hard" adjustment. The IAC is the soft adjustment that works around the inputs of the PCM to finely control idle RPM whether it is 10* or 100* with the AC blasting. If it sticks shut, or is not able to cycle I could see that causing stalling issues.

You really need to scan it for codes though. And if no codes are present, take it for a drive with a scan tool hooked up to datastream it and see what the sensors are reading ...

MDZ28

I went up to scan the car today. It started up and ran just fine, so I drove it home. It didn't have any problems on the ride home and there are no codes.

however when we checked the fuel pressure it was 22psi which to my understanding is low and should be around 36psi.

My mechanic still thinks its the fuel pump and said the fuel pump may drop in psi as the car heats up; causing the stalling.


any ideas?

Injuneer

At idle, you need 43.5 psi, with the vacuum compensation line off the fuel pressure regulator. GM specs accept anything within the range of 41-47 psi. Reattach the vacuum compensation line. Pressure should drop proportional to intake manifold vacuum, about an 8-10 psi drop from the "no vacuum" reading, with a stock cam. Less drop with a more aggressive cam.

Now... you have to take it out on the road under max load (WOT, above 5,000 RPM), with the pressure gauge taped to the windshield. Pressure should not drop below 40 psi.

Low pressure can also be the result of a faulty fuel pressure regulator, leaks in the flex line in the tank, from the pump to the sending unit, or a seriously plugged fuel filter. IT is also possible for the pump to heat soak, and lose pressure.

MDZ28

I think what I'm going to do is instal a new fuel pump and filter and go from there. I'm no where even close to the psi reading I need.

Thanks for all the advice, I appreciate your help immensely.

MDZ28

one more quick question so I know what I'm up against...

will I have to drop the gas tank to access the fuel pump or is there an easier way to get to it?

Injuneer

Did you check the fuel pressure regulator vacuum line for fuel?

There is a "sticky" thread at the top of the "Fuel and Ignition" forum with info on cutting a "hatch" to access the fuel pump.

MDZ28

Sorry for the no reply.....

I have been very busy at work and fixing another issue with the car that just popped up. While diagnosing the fuel pump problem, the water pump started to spew coolant.

I replaced the water pump yesterday and the fuel pump will have to wait until the weekend.

to answer your question, yes we did check the fuel pressure regulator valve and there was no fuel.


I will update this thread when I instal the fuel pump. Hopefully it fixes my fuel pressure issues

HardcoreRM125

Probably was sputtering as the Waterpump has a weep hole. This uhh, was one of GM's more intelligent moves to put it over the VERY water-unfriendly Opti-Spark distributor. If you didn't put a new WP in yet, maybe hold off and test that Opti out. I am banking on that being the case.

Bottom line if it got wet and is causing the misfire - it likely won't "clear up" on its own. You have about a 1% chance of it if the Opti is causing the problems now...

Don't buy ANY other brand, including MSD. Get a AC Delco. They seem to be the most reliable units out of all of them. Shop around ... but be VERY careful with feeBay.



Joe

MDZ28

I too thought it may be the opti but i was having the issue with the low fuel pressure before the water pump issue. The opti did get pretty wet from the spewing coolant but I feel like it would get just as wet driving through a puddle on a rainy day. Not too sure though.

(It does seem like a pretty dumb idea for GM to put the opti which isn't water friendly right under the water pumps weep hole).

I hope to god however that it isn't my opti because I literally just got done putting it all back together.

I have a spare opti but I really don't feel like reversing everything I just did.

I will install the new fuel pump and if it still sputters with the correct fuel pressure I will look into replacing the opti.

Injuneer

Did you ever check the fuel pressure with the engine under max load?

GaryDoug

You may want to consider doing the weep hole mod the next time the pump is off.

MDZ28

I did not however with it only being 22psi at idle there's obviously something wrong with my fuel pressure.

Ill look that up, seems like a smart idea.