Rough Idle - '93 1UZ

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New Member
Cambridgeshire, UK
Hi all,

Over the weekend I removed the inlet manifold and replaced the gaskets for the lower manifold where it meets the cylinder heads. I didn't remove the injectors or fuel rails as I left them attached to the lower manifold and removed them all as one unit.

Since reassembling it all and starting it up it has a REALLY rough Idle. Revs were around 250-300 RPM, the exhaust fumes stank of fuel, it didn't sound like it was running on all 8 cylinders and it normally stalled. I have checked all of the vacuum lines and wiring to the injectors and they are all present and correct This evening I disconnected the MAF and it ran better then but not perfect - revs were up to around 1000 RPM, it was smoother, sounded like it was running on all 8 and it had some trouble settling but eventually it did so. I reconnected the MAF (while the engine was running) and in immediately reverted back to the low revs, struggling, etc.

Before I start buying replacement parts, does this sound like the MAF has failed/is failing or is disconnecting the MAF merely "patching" another problem?

Any help would be greatly appreciated as prior to me touching the inlet manifold, it ran perfectly fine first time, every time.



Well-Known Member
Hamilton. New Zealand
I would think unplugging the Maf is just masking the issue as the default map is quite rich. I would suspect an Air leak but diagnosing it the best place to start. I would dust some engine start or carb clean around the manifold. If it makes a difference then thats where the leak is. Also why did you not change the injector seals? The lower seals go hard causing slight hesitiations at low speed.