I have a 75 1.8L it runs good for the first 10 min lots of pull and power. after about 10min it starts to buck on off rpms dont change, But it hits a big dead spot. and if you keep going it just gets worst. If you puch the motor over 3500 rpms it gets a little more normal.
Now get this let it sit for a cooldown lets say 30min, you start it up and go for about 10-15min, and than its back, Bucking very consistent. It feels like its running out of gas but its not, and this is the same problem 5 times in a roll now.
I did a vavle adj, checked points and wires and plugs. but still no differance. changed out coil. checked with carb cleaner for vac lecks. and checeked vac at vacum advance on both sides of Dist, Now I am a little lost, I now 1.7 and 2.0 but this is my first time owning two 1.8L.
Will take any tips that come my way. Thanks

Does it buck if you are holding the throttle steady? If you floor it does it accelerate and the buckling goes away?


Maybe your TPS is scored or trigger contacts are worn. Try unplugging the electrical connection to the TPS when its warmed up and see what happens, easy test. The acceleration will lag but see if the bucking stops.

but that's just a guess.....good luck

Isn't that the classic symptoms of the head temp sensor gone bad?
Or was it the Thermo-time sensor?


One of the two........
:-)

Don

i have experienced various similar issues with my 1.8. in one case, my spark plug wires were toast, and replacing them fixed the problem. more recently, there's been a 'hiccup' when the rpm gets up in the 3800-4500 range. i replaced the plugs with new bosch platinums and the problem was solved!

ymmv of course, but i'd check those two items. also check your vacuum lines.

~a

Check the resistor pack for "corrosion" on the leads where they connect to the resistors. Could be they are heating up and the resistors are losing connection.

The TPS contacts can be cleaned. A lot of time oil and gunk gets in there. Remove it, pry the cover off (look for tabs) and spray some contact cleaner on there. I doubt this is it, but it's always good to clean that baby.

CHT sensor sounds like it's going bad.

Spark plug wires. Could be heating up and loosing connection

I would check those four things.

Heck.. throw a new set of plugs in in too.

Throw an ohm meter on your CHT sensor. One lead to the sensor output when disconnected from the system and one end to ground. if it doesnt match up with 5% of what the reading is supposed to be at that temp u found your problem. If possible you can try and do an in circuit test with the car running and watch the impedence of the CHT when its connected to the ECU. that might tell you something.

Thanks for the tips to date guys. I will be working on it this weekend and will post an update. What is the ,rissitor pack, and where is it?
Thanks. also what is the big relay doing near the battery?

Big relay near the battery? This may be the resistor pack. It should have five copper wires coming from it (with clear protective coating on the wires). It's a rectangular metal block with four big-ass resistors inside.

Perhaps take a pic and post what you are looking at.

Looks kinda like this...

Strip all of that ridiculous FI stuff out of there and throw it away. Then you can get a Weber progressive and be miserable like the rest of us that got tired of our erratic FI stuff and threw it away. At least I threw mine out in the late 80's b4 the internet and all of this free, mostly accurate, advice. Damn, I miss the 30-35 mpg I was getting. Go here (http://www.icbm.org/erkson/personal/914-73index.htm) and look at the FI diagnosing manual. Wish this had been available in the late 80's Good luck, TT