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Discussion Starter · #1 ·
does anyone know how to tune the 1992 4ze1? seems to run like crap no matter what i do and only 160k on the clock? all hoses are good and distributor good. plugs new and throttle sensor new. that throttle body tho??? seriously wtf?. drives fine but backing down to idle and at idle it cant make up its mind what it wants to do?? gotta be something simple at such low kms?? getting sick of being jerked and jolted while trying to drive in town?
 

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What have you checked? Have you checked for vacuum leaks? That engine is susceptible to vacuum leaks, and when there is one present it will not run well.
 

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Second above post. I had similar issues with my ITEC and finally just got rid of it and went with a weber carb system. It's going on 4 years now with zero issues running. I installed a vacuum gauge in my dash and it's nice to see how the engine affects engine vacuum. Even pulling out my manual choke affects my engine vacuum reading. It would be interesting to see what a gauge would read when your engine is running like crap. There are loads of posts here that point to vacuum problems. One area to easily check is to see if there is a hole in the solid portion of the intake tube where it is routed over the valve cover. Sometimes they will rub a hole in that tube, and it will introduce air that is not measured into the system and the engine will run like crap.
 

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What temp thermostat do you have?? the 190-195 are too hot, you need to run 180 degree. the truck will try to cool itself down with engine idle hunting if its too hot.....
 

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1. Please be more descriptive on your "low rpm" issues and "in-town jerking"
2. While it often causes high idle, how closely did you check the smaller vacuum hoses? They tend to crack at the ends causing vacuum leaks. Sure all hoses are routed correctly?
3. Have you checked the EGR valve? Leaking EGR can cause rough idle - carbon buildup. What about PCV valve - just because it rattles doesn't mean it's good.
4. (BIGGIE) have you adjusted or checked adjustment on the valves? Compression check suggested.
5. What do your spark plugs look like?

Dennis
 

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Discussion Starter · #6 ·
Well ill be buggered... a whole lotta jerkin and spluttering from a coupla tight valves😒. I will never talk crap about hydraulic tappets again😁. So much work keepin this old thing running 😢
 

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Well ill be buggered... a whole lotta jerkin and spluttering from a coupla tight valves😒. I will never talk crap about hydraulic tappets again😁. So much work keepin this old thing running 😢
They also stop running if they don’t have fuel in them. Silly I know…
 
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