1998 Chevy tracker 101, 000 miles.
It runs rougher and low power when cold. When warm it surges in 1st and 2nd if you drive it easy....but does not if you keep the rpm 3 to 4k when shifting. When warm it won't hold highway speed at times of 65 to 70 mph. Also when it does hold speed it won't once i turn the AC on.
Mas and map sensors changed last year. Threw the egr code 2x but mechanic said it was alright. I took it to a second mechanic who said compression is low on one cylinder (120 when others are 190...I assume that's a metric measurement). Do you think its a bad cylinder? Problem with head or vavles on that cylinder? I also had someone suggest that the timing belt may have jumped a cog....that if it was a bad cylinder it would run like crap all the time.
Other background its my snowbird vehicle so its often parked for 8 months per year. This winter i put 3500 miles on her. Its in mint condition body wise so even if it needs an engine ill likely fix when I save up some $$$$.
Thanks in advance for your input
Check your egr valve to make sure it’s not sticking open… or the diaphragm is blown out… ( common issue, bad design)
I know you said mechanic said the egr is fine, but I’ve seen the same exact issue because the EGR will get caked up with carbon, won’t seal when cold, but once warmed up it will…. Eventually it will get worse but at this stage it’s the cold start issue…
If that’s not it than outside of a compression and leak down test, I’d check KV voltage at each plug…
Compression is like blood pressure for people, it is the base for everything else to work right…. 90psi is min for an engine to even run, you should see somewhere around 120-140psi to look elsewhere for the issue… all cyls should be within 5-10psi if each other… if one is really low, or really high you have another issue, could be a valve adjustment, bent pushrod, etc… but first you need to know compression.
@rpmxtreme please copy your comment above into answers section. Thank you.
The mechanic should have been able to determine the cause of the low compression with wet vs. dry compression tests and a leakdown test.
It has timing chain, not a timing belt. If there is a slight rattling noise for a second or two at cold start up, it's time to replace it. It is a psi measurement, not metric on the compression.
If it has 1.6 G16B engine, it has a timing belt.
(120 when others are 190...I assume that's a metric measurement)
Those pressures look like they were measured with pounds per square inch units.
Metric would be in kilopascals and the numbers would be around the 600's
It runs rougher and low power when cold
In this situation I would get a diagnostic readout, and make sure all engine parameters look normal.
