350 wont go past 3k rpms

[Kocher93]

So my 1989 350 TBI won't go past 3k rpms. There is no loss of power, it just won't go past 3k rpms. Timing light says its good, new cap, rotor, wires and plugs. I'm thinking vacuum leak? It also does some weird surging thing while idling. Every other second it will vary rpms, a very slow lope. Any ideas on this? Wires confuse me

 

[Deuling]

Wiped cam lobe? Check oil and cut open filter for metal shavings?

 

[ryoken]

checked it for codes? sounds like an IAC issue...

 

[Kocher93]

Oil is good, motor is actually in amazing shape for 250k. Just a lot of things going bad lately. So for checking codes? How would one do this? and for an IAC is it something
I can replace or clean? I'm terrible at the whole TBI thing, I grew up on carbs so I'm steppin where I somewhat fear to tread.

 

[ryoken]

put a paper clip in terminal A and B on the ALDL connector under the dash... than turn the key on.. the SES light will flash morse code.. oh, here, read this...

http://www.cfm-tech.com/gm_tbi_trouble_codes.htm

the IAC is very easy to get to on the side of the tbi..

it can be cleaned, but many people advise against it.. but it can help in a pinch... does it start with no throttle?

 

[Kocher93]

Yea, starts and drives fine. Just wont go over 3k rpms and does a weird loping, pulsing idle.

 

[63chevyll]

Plugged exhaust?

 

[Kocher93]

Just checked the codes (that was cool!) And no codes, just 12.

 

[eagle mark]

3000 RPM issues are not IAC, idle issues possibly.

It is still pointing to an ignition issue which is common on these high mile engines. Distributor Reference Pulse is sent to ECM and fires injectors, if it is off so is idle.

If this is not a faulty or poor quality EST (module in distributor)? Take off distributor cap, see if there is play in shaft or slop in worn out gear or look in the reluctor wheel for corrosion, rust etc.. and look at black area or rotor wheel for cracks on black/magnet inbetween the metal star saped points!

250K? On same distributor? Just buy a Delco replacement, not a cheap chinese or eBay POS!

250K? On same timing chain? Do you have any idea how much slack that has? This very much effects engine performance.

Or don't rev a 250K motor that high unless your looking to replace sooner then soon...

 

[Kocher93]

Okay this one makes sense. The timing chain is fine, that's one of the first things that was replaced. My Distributor does have rust, play, slop and just general age to it. I was looking at buying a DUI distributor since I'm going to do a complete overhaul soon. Any thoughts on these?

 

[eagle mark]

No reason for DUI? Just put back what was there.

 

[Kocher93]

So in a slop sense, does that mean in rotation? It is very rusty and does click back and forth if I try to rotate it

 

[eagle mark]

Could be slop in shaft or slop in gear being worn. Will also find major green goop on pickup coil and plug to EST. Probably the cracks on reluctor wheel.

Besides differences in the EST module from aftermarket which have been found up to 11 degrees off in timing... if they work. DUI I have seen are large cap and EST is differant wiring and also has differant Spark Latency, so if you install a large cap HEI over small Cap EFI distributor you need to rewire and change Spark Latency in Chip/Bin file.

To easy to put a great distributor back in. Real GM Delco replacements are available. Just google 1103952 distributor and you'll get tons of results. I just got one from Scogin Dickey.