What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

*UPDATE! 1987 Chevy Blazer *rough idle* Please help!

K

kphx87blazer

Registered Member
Joined
Feb 2, 2009
Posts
26
Reaction score
0
Location
phx
Hello,

Long time lurker, first time poster. I searched through some other recent posts.

Anyways...

I was driving a 1993 5.7 IFS Blazer but picked up a solid axle 87 blazer off craigslist. The thing looks great, very clean. The previous owner said a lot of engine upgrades were done ie "cams" and stuff. I dont really know about all this stuff yet but im learning. Its got aftermarket exhaust and its very clean. i figure its got about 160,000+ on it. The truck apparently "sat for 6 months" prior to the sale.


Anyways, The thing has good oil pressure, runs great at highway speeds. But while sitting at a stoplight or pulling into the garage, with the foot on the brake it stumbles, runs really rough and almost stalls. It did stall once but started right back up. Putting it in neutral or park increases the idle and solves the problem somewhat but still runs a bit rough but not near as bad. The truck came with a half tank of gas and I filled the tank right after purchase. So the gas is still in there.

My plan is this:

**Change the spark plugs, wireset, distributor, cap and rotor. Change the fuel filter also.

The air filter came with the top that was quite a bit smaller than the rest of the assembly, so i went to the junkyard and bought the top to fit the entire assembly. Put in a new air filter.

So am i on the right track?

My buddy says the idle may be turned down to low. But you cant just adjust it on this engine. Dont you need a snapon tuner or something?

I thought about vaccuum lines. But Im sorry to admit, I dont have a fekin clue as to where the vaccuum lines are. Does anyone know where I can get some pictures of where the vaccuum lines are?

What about the 02 sensor? Where is it located?

Am I on the right track? Any other ideas?

YOUR COMMENTS ARE APPRECIATED!!!!!

I just want a nice s-m-o-o-t-h idle or am I asking to much from a vehicle thats 20+years old?
 
Last edited:
i would start with vacuum lines, also the throttle body gasket a big problem on tbi and it only costs like 2 bucks and takes 5 min to replace, if its a vacuum leak, spray around with carb spray with the engine running if it changes/stalls u found the leak, tip avoid the wires if they are bad it will ignite the carb spray. this is where i would start cheap and easy.
 
also the tune up stuff, i dont know if it will help, but it definitly wont hurt, and isnt a bad idea if u dont know when it was done last. does it do it when u first start it up too? if so it isnt your oxy sensor cus that doesnt come into play untill your truck warms up and it goes into closed loop, but replacing that wouldnt hurt either, over time an egg shell like crap forms over the ceramic, the sensor still reads but i dont see how it can be really accurate, time being like 100,000
 
check. i will replace the throttle body gasket. now where do i spray with the carb cleaner? around the throttle body? I

t always starts right up. Its a little rough on start up, but once i get going and stop at a stop light a few miles down the road, it starts acting up.

Where is the o2 sensor located?

A buddy also suggested it might be the brake booster. your thoughts?

thanks for the help.
 
02 sensor, is on the passenger exhaust manifold i believe, the fact that it doesnt do it till u drive it a little while before it acts up pushes me away from the vacuum leak a little bit but i wouldnt exclude, and yes u spray the carp spray around the throttle body area.
 
blazer-the cam issue...thats what a few buddies here are saying. but is it possible to move the idle up a bit to eliminate the rough idle? do i need a computer to increase the idle. or is this something i have to live with? i just want a smooth idling truck!

74- thanks for all the advice. great info. if my o2 sensor was bad, wouldnt the computer throw some codes or something?

*in fact there is no check engine light on at all!!! heck, maybe the light doesnt work!

any thoughts on the brake booster?

so tonight ill tackle the following

1 new fuel filter.
2 new spark plugs and wireset.
3 new cap and rotor.
4 new tbi gasket.
5 new cap and rotor
6 check for vaccuum leaks. still a bit confused on this one.
7 change out o2 sensor.

hopefully, god willing, this will fix the prob.

am i missing anything? any more suggestions?
many thanks
 
is there not an idle screw that you can screw in to hold the throttle open more...down by the base that the throttle stops against at idle?
 
blazer- nope. no screw. freinds are telling me that the idle is controled by the computer and i need some special computer hookup to change the settings. thats way the hell outta my league.

copied from the email the seller sent me prior to buying the blazer.

"Engine had an mild rv cam/lifers/emission legal headers added almost two years go"
 
nope. i thought that was all controlled by the computer and was not able to be adjusted.
 
okay. there does not appear to be any vaccuum leaks. in addition, if it matters any, i drove it around a bit to replicate the problem again. Again, at a stoplight it was idling rough and "surging".

any thoughts?
 
you can move the timing by turning the hei in the block, grab the top and try to turn it, the hold down clamp maybe lose letting the distributor vibrate and turn
 
i cant remember how to set the base idle, but i will look it up at work today, i know the screw to do it is a torx bit and its on the front drivers side of the throttle body, usually covered by a small metal cap, u have to pry that out to adjust it, the cap might not be there if someone else adjusted it.

by the way some cams can play havoc on tbi systems, i doubt as though its the brake booster, but anything is possible. checking the timing might not be bad, do u have a timing light? also if u have a friend with a od1 computer it might not be a bad idea to get into your computer and see if anything is reading wrong.

personally i had a problem like this, i chased it for a while and finally i just turned up the idle just a tad, i figured the cam the po installed wasnt the best.
 
Don't mess with the factory idle settings. That will cause problems somewhere else. Find the root cause and fix that.

Timing can be checked with a regular timing light, sticker on the core support should show the base timing, which is checked with the ESC connector disconnected, which is a single wire (tan or brown IIRC) connector near the brake booster, partially sticking out of the wire loom.

Check engine light should come on when the key is moved to "run", and once you start it, should go out. if the light does not come on, you need to fix that first.
 
Had the same problem on my '89 after I installed headers, put a heated O2 sensor on it and it fixed my problems.
 
Well I changed the TBI gasket, new spark plugs, wire set, cap and rotor and fuel filter.

Started it up. Wouldny start! Drats! I messed up on wires. So I redid the wires on the distribitor cap and it finally started.

Anyways...

No improvement!!!! Emphasis on the word "no".


The vaccuum lines appear to be okay. Is there a test that can be ran so I can be 100% sure I dont have a vaccuum leak?

Any more ideas???

thanks
 
kphx87blazer said:
Hello,

Long time lurker, first time poster. I searched through some other recent posts.

Anyways...

I was driving a 1993 5.7 IFS Blazer but picked up a solid axle 87 blazer off craigslist. The thing looks great, very clean. The previous owner said a lot of engine upgrades were done ie "cams" and stuff. I dont really know about all this stuff yet but im learning. Its got aftermarket exhaust and its very clean. i figure its got about 160,000+ on it. The truck apparently "sat for 6 months" prior to the sale.


Anyways, The thing has good oil pressure, runs great at highway speeds. But while sitting at a stoplight or pulling into the garage, with the foot on the brake it stumbles, runs really rough and almost stalls. It did stall once but started right back up. Putting it in neutral or park increases the idle and solves the problem somewhat but still runs a bit rough but not near as bad. The truck came with a half tank of gas and I filled the tank right after purchase. So the gas is still in there.

My plan is this:

**Change the spark plugs, wireset, distributor, cap and rotor. Change the fuel filter also.

The air filter came with the top that was quite a bit smaller than the rest of the assembly, so i went to the junkyard and bought the top to fit the entire assembly. Put in a new air filter.

So am i on the right track?

My buddy says the idle may be turned down to low. But you cant just adjust it on this engine. Dont you need a snapon tuner or something?

I thought about vaccuum lines. But Im sorry to admit, I dont have a fekin clue as to where the vaccuum lines are. Does anyone know where I can get some pictures of where the vaccuum lines are?

What about the 02 sensor? Where is it located?

Am I on the right track? Any other ideas?

YOUR COMMENTS ARE APPRECIATED!!!!!

I just want a nice s-m-o-o-t-h idle or am I asking to much from a vehicle thats 20+years old?
Click to expand...


I'm thinking you need a new chip..... I mean, if I take MY 87 and I go to Edelbrock and buy their heads, cam and TBI intake, they will give me a new chip for free...so I'm thinking if they do that, that its probaly needed
 
I had this problem on mine and it bothered me so much Frickin PISSED me off, but I got used to it. To the point that it went away and Im not sure which repair fixed it. When I got rid of the CAT and put in new exhaust it seemed to get better, Then the rest was mostly tune ups and getting the inujectors replaced. I also ended up replacing my fuel tank as the baffles inside were broken and that was causing some surging and then dying. I wish I could help you better. Proper ignition spark and or spark plugs is a big thing. Just the other day it did that to me and died I realized I had my foot on the throttle pedal but not really on it and it was like it got fuel but not what it needed. So it died Hope something I rambled on helps or gives you an idea.
 
The thing runs pretty smooth in PARK but otherwise while in drive at a stoplight its pretty bad. Rough and surging.



Is the "emissions control" sticker under the hood the same thing as the vaccuum lines.

thanks
 
You must log in or register to reply here.

Latest Posts

Top Bottom