95 blazer runs real rough

I have been working on my blazer for about a month's. I have replace several new parts.

FUEL PUMP This will be second one
PLUGS & WIRES
CAP
TROTTLE BODY SENSOR
O2 SENSOR BANK 1
Coolant temp sensor
EGR Value
fuel pressure regulator


We have check the fuel pressure it seems to be okay. We also hook it up to a computer it came up with a random misfire po300. The truck run at a idle really well. However, when you take it down the road t falls on its face. When you push to the floor it gets up and goes but runs real rough. We are losing fuel pressure. We replaced the fuel pressure regulator now it will not start. So we also replace the fuel pump again thinking that we got a bad one. It still will not start please Help.

Does anyone have a clue PLEASE.

:runaround:

The fuel pressure regulator is connectd to the spider assembly under he plenum. Get a fuel pressure gauge and check the pressure at the schraeder valve on the drivers side an the back of the plenum. You should have 60psi. Watch the gauge after you shut it down. It should maintain pressure for a whilel

I am having simmillar problems. My truck Idles great. But when i start going between 2000 and 3500 rpm my truck bucks and skips, it sounds like weak fuel pressure. I put on new wires plugs cap and rotor. but im getting the missfire code. I need help. IM going to check the fuel pressure like blazerbob says

Thank you for responding. I check the fuel pressure it was not okay. So replace the fuel pump again and the fuel pressure regulator. It started for a few minutes then died now it will not restart. Now what do we look for?

What engine code?
What is the fuel presure reading?
Does it have good hot blue spark to all spark plugs?
Will it start with a shot of carb cleaner?

We did not have any codes except the po300 random misfire. Yes there spark to all the plugs. The fuel pressure is now between 60-62psi and stays. No it will not start no matter what we do.

Now they think that it is the control module ing., camshaft sensor, or the crankshaft sensor. I can not keep putting money in this truck.

Why would all these sensor go bad at once?

Why would all these sensor go bad at once?

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.


Got compression?
Pull plugs and check compression and see if plugs are wet or dry on the ends.
Is the plug wiring right?
Is it a flat top dist or old style dist cap?
What is the engine vacuum readings at idle and at 2K rpm?

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.


Got compression?
Pull plugs and check compression and see if plugs are wet or dry on the ends.
Is the plug wiring right?
Is it a flat top dist or old style dist cap?
What is the engine vacuum readings at idle and at 2K rpm?

Yes the truck has compression and the plugs are wet. The truck has a flat top dist. Yes the wiring is right as well. I do not know of any vaccum leaks because the truck will not start.

The truck ran up to just a few days ago. We put the parts on one at a time. Everything was okay with the starting until we put on the new fuel regulator. And then it started for a few minutes then died. We found there was a vacumm leaks and fix it. The truck started again for a few seconds and died. It sound go no hesitation or nothing it just died. It has not started since. And still did not have fuel pressure so we put the second fuel pump on got the fuel pressure back to 60-62psi and stays. But truck will not start.

Is it getting good hot blue spark to all plugs?

Thank you for responding. I check the fuel pressure it was not okay. So replace the fuel pump again and the fuel pressure regulator. It started for a few minutes then died now it will not restart. Now what do we look for?

What fuel pressure did you check?
Static motor off?
Idle with vacuum off of FP regulator?
Idle with vacuum ON FPR?
Pedal down test in second gear - guage taped to windshield, to check for acceleration enrichment / vacuum response???

Random misfire shouldn't be too hard to trace. Start from the rotor, and work back to coil, ignition module, etc. Inspect first!

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.


Yup.

Get it out of his hands YESTERDAY, and get it elsewhere.

If a mechanic cannot trace a 'random misfire', he is NOT a mechanic, he's a fisherman.

Is it getting good hot blue spark to all plugs?

Yes it is getting good fire.

I guess you can take the control module ing. can be tested so I am going to have it tested.

I guess you can take the control module ing. can be tested so I am going to have it tested.
Let us know how it does.
Good luck

Well guys I had the ign. control module tested was okay coil okay all getting good spark. We had to change the idle air control module. Now the truck runs with no hesitate or erratiac spudder. It runs really good for about 30 miles and it just died put it into nutreal started right back up. I got a little furstrated so I stomped it to the floor ran great. Went a few more miles it did it again. Started right up keep going. Truck will start right up everytime. Now I no I have to have a bad ground but where should I start. Not got a clue about grounds.

Excellent - it will start now. Do a vacuum leak test, and post back.

Loping idle is vacuum leak. 30 year old lawnmower, or a new car on the lot. If it sucks air where it ain't supposed to, it lopes.

Brick on pedal, block TB arm, anything to get a STEADY idle. 1200rpms or so... Feed starting fluid spray, A LITTLE AT A TIME, EVERYWHERE. RPM increase is the leak.

In a tough spot to pinpoint? Light a book of matches, blow it out while the heads are burnin', and feed the smoke to the leak.

That's a free test.

Then test the fuel pressure as posted before...

Post back results...

Well guys I had the ign. control module tested was okay coil okay all getting good spark. We had to change the idle air control module. Now the truck runs with no hesitate or erratiac spudder. It runs really good for about 30 miles and it just died put it into nutreal started right back up. I got a little furstrated so I stomped it to the floor ran great. Went a few more miles it did it again. Started right up keep going. Truck will start right up everytime. Now I no I have to have a bad ground but where should I start. Not got a clue about grounds.

Proper testing.
When it quits are you losing spark or fuel pressure?
What engine like what engine or engine code?
Old style dist or new flat top style?
Any check engine lights coming on or engine codes stored in VCM?

Okay guys I found the problem The ecm ing. and ecm batt. fuses that runs the computer where not getting a good conection. So when you hite a bump it would die. I tighten the conecter and it runs fine. Who would have taught $1.00 fuses could cause so many troubles and money. Thank You for all your help.