No, I am not getting any back firing.

The the truck just seems to be extremly hesitant.

I plan on doing a leak down test. If time permits I will do this on Sunday. I am really running out of ideas as what to check.

If the leak down test proves ok, I guess I need to look back at sensors?

baylesr

 

Sorry. Guess I got confused there.

 

Stepman,

I am not for sure what that post is about either..

The way I tested my fuel injectors, was to take them out of the truck and had them flow tested at a local shop. The shop has a fuel rail they attatch them to and signals them to inject fuel. The fuel is then measured. I am not for sure how much fuel was measured the shop just told me they checked out to an equivalent 9000 RPMs.

I have heard of using a stethoscope and listening to injectors to see if they are opening and closing, however this will not tell you if they are plugged and not injecting fuel. I orginally tried listening and decided to go to a higher step of diagnosing.

 

How about checking the MAP sensor? Symptoms are close to a those of a malfunctioning MAP. Remember, not all problems will trip a code but will cause drivability troubles.

 

Do you have something drawing vacuum from a sourse around #2? Maybe an accy with a leak? Or possibly an intake leak.

 

Another update:

Brrossi, I checked the MAP sensor tonight. Everything checked out OK

Stepman, I do not have any accesories on the truck, unless you count a rubber bed mate . But I will check for a vacum leak around cylinder 2.

My plan was to do a leak down test last Sunday. But as things usually go I did not have enough time to perform the test properly so I thought I would just wait. I new plan is to run the leak down and compression test Saturday night. I am not for sure if the two tests are required. I will just assume the more information I can get the better.

So if things go well I will run all three tests and post the results as soon as I get them.

Thanks for the help and ideas

 

After rereading this I got a couple more ideas for you to keep you busy this weekend but, I forgot half of them already. When you pulled the line off the EGR did you notice any vacuum there?Where is the valve mounted and where does the line run to? Does your dist have a vacuum advance?

 

I would replace the distributor cap, I have had brand new ones cause the problems you are describing. It may look alright per a visual inspection but, can indeed be bad. I would replace it and the rotor with an expensive set from napa, as they seem to be the best. I have learned that it does not pay to go the cheap route on ignition/electrical parts. I would also check to make sure your brake booster isn't leaking, and make sure all the vaccum lines on the engine are ain good shape. I had a few that I thought were good until I went to pull them off to check them, and they crumbled.

 

Sounds like a vacuum leak to me, have you checked for that? I understand you can get them between the upper and inner intakes, or maybe a broken vauum line?

 

Try unhooking the vacuum to your fuel pressure regulator. It may be a fuel pump. Does your '90 have 2 high pressure pumps ( one in each tank? or does it have the old setup with 3 pumps, (2 low pressure in the tanks, and one on the frame rail)?

Anyway, see if that makes any difference. unhooking the FPR vacuum (plug the line ) will give the fuel rail full pressure. If it cures your problem, replace the FPR and recheck the fuel pressure with a gauge.

Good luck.

 

fishin1976

I have three questions:

After I disconnect the FPR is the pressure on the fuel injectors the same as I measure from the schrader valve?

Do you think this high pressure would hurt the fuel injectors?

Ok I only had two questions.

Thanks for the input, I will have a busy weekend with all the suggestions. Hopefully I will finally find the problem..

baylesr

 

The high fuel pressure will not hurt the injectors but will make it run rich. Does the exhaust smell rich?

Have you sprayed starting fluid or something similar around the intake and vacuum lines (this is the only way to check - visual inspection only works for obvious problems). It still sounds like a vacuum leak.

 

Here is the newest update.

1. Checked the FPR. everything is fine. Used a fuel pressure gage along with observing engine. Engine ran the same, and fuel pressure went up when vacum line disconnected.

2. Distributor cap. Replaced in August with New expensive NAPA one. I to have played the game cheap parts make things worse. I might go buy a Motorcraft one just to make sure.

3. I used a vacum guage to check the vacum on the truck. I did not feel like squirting starting fluids ect around the engine compartment. I am not for sure if this will tell me about a vacum leak or not though. I believe I had about 22-24 in lbs (I think that is what it is measured in) and the gauge read steady.

Should I go ahead and use the spray down method?

4. I performed a leak down test... and the results are:

1. 10% leak down
2. 13%
3. 17.3%
4. 1.3%
5. 13%
6. 13%

I am not for sure what to make of this. I know that from the instructions with the gauges that anything between 10%-15% should be looked into. But the truck does not smoke or use oil. So I really do not know what to do with this information. I really expected to see one cylinder readings extremly different. I was hoping cylinder 2 would be really off. Because the spark plug always looks new in this cylinder.

I will keep everyone posted on the saga...

 

Those are actually pretty decent numbers on your leakage. I consider 10-15 normal and wouldn't worry about it You will find that it 's probably going past the rings into the crankcase and that much will easily be picked up by the PCV.
I still think this is either the EGR or a vacuum leak. Does your EGR have vacuum at idle? Does it hold a vacuum? If you can get your finger under it rev the motor and feel for it to open and close.

 

Have the same problem, have done most of the same things. Truck just runs like it's missing out at idle and slight throttle as you run down the road. It'll run a little different with the air on so I guess it's just vacuum leak that I can't find.