Cant figure out my Blazer

[tenderfoot1877]

for the last two months, my Blazer has been giving me problems. When I start it in the morning, it runs OK, but after it warms up, forget it. It runs like crap. After its warm, and I press the gas to either pass some one or to just accelorate, it bogs down almost as if it isn't getting enough gas. The injectors are fine, Ive changed out the PCV valve, the EGR valve, spark plugs, rotor, cap, fuel filter, gutted the Cad. converter cleaned the throttle body, and replaced the throttle possiton censor. I DONT KNOW WHAT ELSE TO DO. PLEASE HELP

 

[warreclipsegst]

Check to make sure your choke isn't sticking closed..

 

[resurrected_jimmy]

My first guess would be a fuel issue as it warms up. As in its running lean and slowly overheating. Fuel filter, timing, fuel pump... ????

 

[tenderfoot1877]

I don't know to much about Throttle Bodies, where is the choke on it?

 

[tenderfoot1877]

maybe the fuel pump, but it gets plenty of fuel so I don't think so

 

[resurrected_jimmy]

I should pay attention to what I read. I doubt choke but its possible I guess. Since its TBI you really need to know the fuel pressure going to the injectors. My next guess would be o2 sensor or TPS (throttle position sensor), I had one behave like this because of the knock sensor.


Is it not throwing any codes? Is your check engine light on?

 

[tenderfoot1877]

my check engine light doesn't work and I just changed the TPS yesterday. I dont know how it would act if the o2 sensor went out so maybe

 

[warreclipsegst]

sorry, didn't know it was TBI. forget the choke post

 

[resurrected_jimmy]

ok, we need to know if its throwing codes. Ummmm, can't help with the check engine light not working I hate dashboards, but if you can get a code reader to tell you if its giving a diagnostic code that would be worth its wieght in gold!!! I don't think you can read OBD I codes without a check engine light (correct me if I'm wrong)

 

[lamberthkp]

i had a problem like that about a month ago , mine ended up being a small vacum leak & the ecm was about dead, it sure would be nice if you could check the codes. good luck!

 

[88-383]

Just throwing out some thoughts. Bogs are usually fuel or timming related. So here's some things to think about.

1) Vacum leaks can be a headache.....
2) Does it bog in nuetral?
3) How does it drive when cold? no bog at all?
4) After the ecm goes closed loop @ 140-160deg the ecm makes decisions about mixture based off readings from the O2 sensor*** prior to going closed loop the ecm runs a warmup program/routine or profile etc...

Engines that dont seem as crisp after going closed loop may be suffering from degraded O2 sensor performance. **I'm asuming we're talking about a totaly stock TBI truck here** headers,custom chips and other mods can also cause similar issues.

The codes can be pulled even though the light doesn't work but you'll have to have a scanner that connects to the ALDL. I'm a TPI sort of guy thats new to TBI.

Good Luck

Kelvin

 

[Russell]

Throwing random parts at TBI does nothing but cost you money. If you are gonna spend money, I'd put that into a new lightbulb for your SES lamp, and check your codes

Start simple, then go from there. Chances are your TPS was just fine as was, and probally set you back a good 40 - 50 bucks.

Hows your timing look? My 89 was at about 14 degrees ATDC (I usually set mine about 5 degrees BTDC) and it was behaving much the same way. Started ok, but had absolutely no power, and would backfire through the throttle body etc. TBI has the ability to adjust the timing electronically, but it still needs the dizzy to be set accurately to be able to base the timing in the prom off something.

Second, check your fuel pressue. If you've got no fuel, you've got no power.

Then check your 02 sensor out. Take it to a local parts house, and have them put the OBDI scanner on. Usually they'll do it for free. Chances are the kid working there will have no idea what he is doing, so yeah, you'll be looking for the 02 sensor to be crossing between .2 and .8 volts on a consistant basis. If it ever sits still at a certain voltage for more than a second, or if it provides no voltage at all and runs the truck in open loop, then the 02 sensor needs replacement.

Last things I'd check would be the MAP, injectors, then knock sensor, and very last would be the EST module, or ECM. ECMs don't just sorta half work, they either do or they don't like most electrical components, lol

 

[sarasotausmc]

I just went through this. After replacing the O2, MAP, Electronic Spark Control and knock sensors, finally got around to the fuel filter. After over $150 in parts, a $2.99 piece fixed the problem. Haynes and Chiltons never mentioned it. Good luck.