i have a 95 suburban 1500,
it wouldn't start about a month ago. it ran fine, parked it, next day it wouldn't start ( in the winter). i replaced the coil, distributor cap and rotor, ignition control modal, spark plugs and spark plug wires. after that it started up fine, drove great for about 5 days, and then it lost all of its power, ( i noticed this about day 3 of 5, and it got worse the next 2 days)

at first (day 3 of 5)it had a little trouble going up hill, then (day 5 of 5) it could barley make it up the driveway, and stalls, runs very rough.
you can rev it up in park or neutral and its fine, but under load it is terrible. as soon as you touch the gas, especially low RPM, it trys to stall. i haven't drove it in about two weeks now, except for testing it out after i did work to it.

i pulled 1 plug and it was running lean, so i started hanging parts ( the truck is pretty new to me and i am ok with putting money into it), but now i am starting to run out of ideas.

so far i replaced the above parts (coil, dizzy cap and rotor, ICM, spark wires and plugs) and also
coolent tempatur sensor
TPS
EGR valve ( the valve wasn't moving, or holding a vaccum, but appeared to be stuck closed)
egr solenoid.
MAP sensor ( had a crack in it, so i just replaced it)
PCV valve
fuel injectors ( new o-rings and washers on them)
fuel pressure regulator
fuel filter
fuel pump & strainer ( i was planing to do the pump this summer anyway, so it didn't go out in the winter)
fuel sending unit ( the fuel line on it broke when i was removing the fuel line from it to do the pump, so i had to replace it).

still no luck. any ideas on what to do next? i think i am going to start testing stuff now instead of just replacing them

to be honest, i don't work on cars much, but i work on motorcycles and small engines a ton. ( i own 9 motorcycles, and do all the work and maintenance on several other ones also. restored a lot of 80's bikes)

 

also no check engine light, and it is obd1, not obd2!

i did also replace the vacuum line between egr -to- solenoid, solenoid -to- throttle body, and Map -to- throttle body.

i have ordered some car tools from amazon(timing light, fuel pressure gauge, vacuum tester), coming hopfully this weekend but here is what i am thinking i should be checking from searching:

check fuel pressure for clogged line or something (even though it should be good with the parts i replaced, still need to verify it)

pull all the plugs and look at them, see if they are all lean, or if one is missing, or what not.

check vacuum reading at map sensor ( test brake booster, didn't seem to run any worse with brake pressed)

check timing (0 degrees at idle, with brown wire unpluged)


anything i am missing or should be testing? i'll let you guys know the results when i get the tests done.

it probably would have been cheaper to take it to the shop at this point, but i need to learn how to fix this truck anyway, and i'd rather spend money on tools then pay a mechanic.

 

i tested the fuel pressure, 14 psi solid.

 

vacuum test, it started out steady at 17.5 inHg at idle, as the engine warmed up, it was at a steady 16 inHg.

when it was warm, and i snapped the throttle, it goes to 0 quickly, up to 17 inHg, then it sits at 15 for a couple seconds, slowly rising back up to 16 and remaining there.

i found out i can't snap the throttle to hard, or it back fires through the throttle body and stalls, or try's to stall, this seems important. ( so pressing the throttle quickly even in park will cause a pop and stall, this seems consistent with running lean i think)

anyway, as far as i can tell, the vacuum readings don't indicate a problem, is that correct?

 

i can cover the exhaust with my bare hand, at idle,

it almost feels like its sucking in a little bit rather then trying to push my hand off, i checked my cat, and it isn't making any weird noise(at idle atleast), but i am thinking that it might be a clogged cat now ( the cat is the last thing getting hot, all the pipe down the line i can touch with my bare hands)

i am going to test it out with some one rev'ing it later to confirm, but it seems like that might be the issue.

 

i hate to bitch and moan, but seriously? no replies?

is this not the right forum for something like this, or did i post wrong place/wrong way?

 

Patience my friend, you probably got everyone straining their brains with all the work you have done already! Change distributor yet??

 

I would run a good scanner on it just incase.

I'm not much of an internal engine guy but it sounds like it's an inside job.

Your getting fuel, air, spark so there's something else making it runn crappy. but if there's no cel...?? That could be out or covered.

I didn't see that you did a compression test yet?

 

can't run a good scanner on it, its od1, not odb2

cel works, just no codes stored.

no comnpression test yet.

 

i have not changed the actual dizzy yet.