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new head gasket and now need help
Topic Started: Feb 18 2010, 02:55 AM (1,726 Views)
sledgehammer
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i just got her backtogether with unburnt but used exhaust valves and new head gasket. I have few concerns i'd like help with

high and surging idle: it idles high but after reving the engine at all as soon as it comes down to idle it surges like highg low high low for like 5 seconds then stays at high, know why????

burnt valve prevention. how can i prevent burnt valves? i read some thing about clogged cats and puking pcv also premium fuel


please help?!

btw i love my first geo fun to drive gonna take a bit to get used to manual steering :)
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rmcelwee
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Idle surges are probably caused by a vacuum leak. Check/replace all your hoses.

Make sure your EGR system is not plugged to keep your valves from burning up.
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lmaopimp
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had the same problem... it seems I installed my pvc bracket in only a way I could - LMAO


ditto on checking the vacuum lines and seal between your head and intake.
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Johnny Mullet
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Fear the Mullet

Also set the ignition timing to 8-10 degrees advance to help prevent burnt valves.
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mwebb
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FOG

if the closed throttle switch in the TPS does not close
system will surge as the ECM does not the throttle is closed and the idle circuitry does not get activated

throttle cable is too tight ? throttle stop was "adjusted / tampered with" ?

OR

vacuum leak
raises idle speed and closed throttle switch tells ECM throttle is closed , but idle is over 1200 rpm so
system activates DECEL FUEL CUTOFF , until RPM drops below 1200 rpm , then system switches fuel back on ,
rpm gets above 1200 rpm and ....
repeat repeat repeat ....
engine surges

OR

the throttle stays open because the bimetallic faST IDLE thing in the throttle body is clogged and does not get hot ...
so
that raises idle speed and closed throttle switch tells ECM throttle is closed , but idle is over 1200 rpm so
system activates DECEL FUEL CUTOFF , until RPM drops below 1200 rpm , then system switches fuel back on ,
rpm gets above 1200 rpm and ....
repeat repeat repeat ....
engine surges
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sledgehammer
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had no egr...... no mount or anything. and how do i set timing advanced? thanks everyone
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Bad Bent
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Facetious Educated Donkey

Yep, my '91 has no EGR either.
You'll need a timing light to adjust the timing accurately.
You'll either plug the vacuum advance lines at the distributor or short the socket that's above the driver's side strut tower (see sticker on hood). Loosen the 2 distributor bolts (slotted) to snug, attach the timing light to the battery and #1 plug wire, aim the 'gun' at the timing marks on the timing belt cover and pull trigger to illuminate the mark on the pulley. You gently tap the Distributor body to rotate it a degree or two until the timing mark on the pulley aligns with the scale on the timing belt cover. Tighten the Dist. down, recheck the timing.

Posted Image Correct hood sticker.

Posted Image

Posted Image
Edited by Bad Bent, Feb 19 2010, 08:28 PM.
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Johnny Mullet
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Fear the Mullet

:gp Bad Bent!
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Bad Bent
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Facetious Educated Donkey

To clarify....

OK, so my '91 has a diagnostic port and it happens to be vacuum advance.
The object is to stop the computer from advancing the timing when you are adjusting it.
I said "You'll either a) plug the vacuum advance lines at the distributor or b) short the socket that's above the driver's side strut tower (see sticker on hood)."

So I have a sticker that says "6o BTDC with disconnected and plugged distributor vacuum hoses" That's what I do. If you do not have a sticker and you have a '91 with vacuum advance then plug the hoses and time the beast.
Part two is if you have electronic advance then jumper the diagnostic plug according to the instructions on the sticker on the hood. This is a CYA statement in case you don't have vacuum advance and want to use my instructions.

FYI I have timed it by plugging the hoses and jumper-ing and not jumper-ing the socket and it did not make any difference. IMHO.

A vacuum advance should be plugged in ANY case.
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Murf 59
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What do your spark plugs look like? Are they white, grey or black? When I did the engine swap in the Rocket. I missed a plug. It went to my map sensor. So it was running way rich. My new plugs were soil black. Once I found the wire I missed. It ran perfect. It was on the fire wall behind the air cleaner.
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sledgehammer
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so i fixed the surge.... it was the tps. fixed high idle..... stop screw. but it smokes really bad. burning a crap load of oil now what is wrong. i replsaced pcv valve. i replaced all valve guide seals. WTH???
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redpepe


hi sh,

good work on the tuning fixes.

i hope i'm wrong but it sounds like the usual 'new head gasket' problem. if the holes in the new gasket were not the right size, as many new gaskets are NOT, then the poorly draining oil accumulates above the valves and passes out the pcv port either to the intake or back through the engine to the exhaust. either route makes clouds of white 'smoke' ..... usually only at higher rpm in my experience but i'm sure there are many variations possible. it's a simple head gasket replacement that should do the trick. there are a few good postings / threads here which will help.
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Memphis metro


Mr Murf 59
Feb 20 2010, 02:20 PM
What do your spark plugs look like? Are they white, grey or black? When I did the engine swap in the Rocket. I missed a plug. It went to my map sensor. So it was running way rich. My new plugs were soil black. Once I found the wire I missed. It ran perfect. It was on the fire wall behind the air cleaner.
Thats what I found wrong with mine yesterday. My plugs kept smoking up and the check engine light was on. I ran the code down and it pointed to the map sensor. I looked over and found the vaccum line off. Not sure if I put it back on after rebuilding it or not. Either way she picked right on up after that. In my experience, map sensors make a huge differance if they are not acting correctly.
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Murf 59
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@enginedoc. I had the same exact problem. Hooked it up, and now it runs like a top
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