87K5Blah

ok, so 1987 K5 blazer with the K series 350, TBI. One day the truck started messing up (couldnt get a better description) and my roommate was barely able to get it home, it had absolutly no go. He had to keep pumping the clutch to get it to move and stay running. So we looked at it the next day and I inspected the throttle bore as we kept it running by constantly playing with the throttle. I notice that the spray pattern on the injectors was very weak, instantly I thought that there was a lack of fuel pressure. My roommate at that time mentioned that he had run the truck dry on several occasions. So we did the cheapest thing and replaced the fuel filter, roommate later mentioned to me as he did it that the fuel was a black color. The problem continued the same, so we swapped out the fuel pump with another we had on hand that had less than 30hours on it, same problem. I went back to the start and looked again at the spray pattern, I noticed this time that the wiring looked a little suspicious, I grabbed the drivers side injector harness and wiggled/pushed it further into the clip, the spray pattern cleaned up a little bit and the truck stayed running as long as I held onto it.

So we replaced both fuel injector clips with new pig tail ends from napa, the spray pattern was looking good now and the truck would stay running. However there was still no power under load or fast depression of the accelerator. We have had no ECM codes up to this point, so I figured well maybe the diaphram on the fuel pressure regulator maybe obstructed or worn out. We pull it off and it didnt look too good but it wasnt bad enough that it should have caused the problem, we replaced it any way. Same problem except now the truck decided that it would not sustain idle anymore. My next thought was that it had to either be the injectors themselves or a bad input from a sensor that was causing this. Tried swapping the injectors only to make things worse, put the old ones back. Ok so maybe a sensor, from my knowledge and experiance the Map or MAF(N/A) sensor have the biggest input on injector pulse width/output. I unplugged the map sensor and we started the truck, it stayed running, sounded better than before and would reach higher rpms then previously with less hesitation. Great so we go down to napa again and get a new map sensor, put it in, I checked the hose to runs to the back of the throttle body to make sure it wasnt clogged and verified that there was vacuum at the TB bung. Same problem we had with the old map sensor now, truck wouldnt stay running un assisted and still had zero power.

Also tried swapping the ECM with another of the same service number only to have the same results as the original.


My question is that after reading my ridiculously long description, what other sensors have a direct affect on the fuel timing/curve besides the map and cooland temp. Has anyone had this problem and know what we should try?

**Edit**
I have starting problem in the topic description, I forgot to mention that the truck as a about 15sec delay between initial start of turning over and actually firing the cyclinders.

golfer

The problem could also be the spark timing. Have you checked or replaced the ignition module or the pickup coil in the distributor?
Do you think that it may be running too rich and flooding ? Could be the temp. sensor.
When it's running rough it could be the EGR.

Just some ideas.